All Of My Java Codes With A Sample Output.docx

Name – M ADHITYA
ALL OF MY Java PROGRAMS
[
Code:
package com.company;//TIP To <b>Run</b> code, press <shortcut actionId="Run"/> or
// click the <icon src="AllIcons.Actions.Execute"/> icon in the gutter.
public class Main {
public static void main(String[] args) {
//TIP Press <shortcut actionId="ShowIntentionActions"/> with your caret at the
highlighted text
// to see how IntelliJ IDEA suggests fixing it.
System.out.println("Hello World");
}
}
Output:
Hello World
]
[
Code:
// storing integer in variable in java and printing
public class Main {
highlighted text
int number = 8; //storing integer
System.out.println(number);
}
}

Output:
8
]
[
Code:
public class Main {
highlighted text
System.out.print("The sum of the numbers is: ");
int num1 = 2;
int num2 = 3;
int num3 = 4;
int sum = num1 + num2 + num3; //sum of three numbers
System.out.print(sum);
}
}
Output:
The sum of the numbers is: 9
Process finished with exit code 0
]
[
Code:
package com.company;
public class CH_04_Literals {
byte age = 34;
System.out.print(age);
char ch = 'A';
float f1 = 5.6f;
double d1 = 5.66D; //By default decimal no. is double so can choose to not
write D or d
long ageDino = 5666666666666666l; //can write capital L
short age3 = 87; //no need to write s for short literal
boolean a = true;
String str = " Adhi";
System.out.print(str);
}
}

Output:
34 Adhi
]
[
Code:
import java.util.Scanner; //Importing external Scanner class(import statement)
public class CH_05_TakingInpu {
System.out.print("Taking Input From the User: ");
Scanner sc = new Scanner(System.in);
System.out.println("enter number 1: ");
int a = sc.nextInt();
int b = sc.nextInt();
int sum = a+b;
System.out.println("the sum of these numbers: ");
}
}
Output:
Taking Input From the User: enter number 1:
2
enter number 2:
3
the sum of these numbers:
5
]

[
Code:
// int a = sc.nextInt();
float a = sc.nextFloat();
// int b = sc.nextInt();
float b = sc.nextFloat();
float sum = a+b;
System.out.println("the sum of these numbers: ");
}
}
Output:
Taking Input From the User: enter number 1:
2
enter number 2:
3
the sum of these numbers:
5.0
]

[
Code:
String str = sc.nextLine(); //nextLine method is used to read whole string
line, and next method is used to only read first word
}
}
Output:
Taking Input From the User: 2
2
]
[
Code:
String str = sc.next();
}
}
Output:
Taking Input From the User: Adhi
Adhi
]

[
Code:
// import java.util.Scanner; //Importing external Scanner class(import statement)
//calculating CGPA of 3 subjects
float sub1 = 45;
float sub2 = 97;
float sub3 = 48;
float cgpa = (sub1 + sub2 + sub3)/30;
System.out.println(cgpa);
}
}
Output:
6.3333335
]
[
Code:
//Taking Name as input and wishing them using string concatenation
System.out.println("What is your name: ");
String name = sc.next();
System.out.println("Hello "+ name + " Have a good day!");
}
}
Output:
What is your name:
M Adhitya
Hello M Have a good day!
]

[
Code:
//Checking if input is Integer or not through Boolean
System.out.println("Enter your number: ");
System.out.println(sc.hasNextInt());
}
}
Output:
Enter your number:
23.8
false
]
[
Code:
public class CWH_CH02_Operators {
int a = 4; //Operators
int b = 6*a;
System.out.println(b);
}
}
Output:
24
]

[
Code:
//int b = 6*a;
int b = 9;
b+=3;
}
}
Output:
12
]
[
Code:
//int b = 6*a;
int b = 9;
b+=3;
System.out.println(6==8);
// = is assignment operator and == is comparison operator
System.out.println(64>9);
}
}
Output:
12
false
true
]

[
Code:
//int b = 6*a;
int b = 9;
b+=3;
System.out.println(6==8);
// = is assignment operator and == is comparison operator
System.out.println(64>9);
// && is logical operator
System.out.println(64>5 && 64>8);
}
}
Output:
12
false
true
true
]
[
Code:
int a = 5*6 - 34/5; //Precedence and Associativity in Java
int b = 34/5 - 60*5;
System.out.println(a);
}
}
Output:
24
-294
]

[
Code:
//Precedence and Associativity in Java
int x = 6;
int y = 1;
int k = x*y/2;
System.out.println(k);
}
}
Output:
3
]
[
Code:
//Precedence and Associativity in Java
int x = 6;
int y = 1;
int k = x*y/2;
int a = 1;
int b = 2;
int c = 3;
int d = (b*b - 4*a*c)/(2*a);
System.out.println(d);
}
}
Output:
3
-4
]

[
Code:
public class CWH_10_resulting_data_type_ps1 {
int a = 654 + 6; //Resulting Data Type by Adding etc. 2 different data type
byte x = 5;
float b= 3.56f + x;
int y = 6;
short z = 8;
}
}
Output:
8.559999
]
[
Code:
/* int a = 654 + 6;
byte x = 5;
float b= 3.56f + x;
int y = 6;
short z = 8;
System.out.println(b);*/
// Increment and Decrement Operators
int i = 56;
System.out.println(i++); // i++ means print i then increment it
System.out.println(i);
System.out.println(++i); // ++i means print increment then print i
}
}

Output:
56
57
58
58
]
[
Code:
int y = 7;
System.out.println(++y*8);
char ch = 'a';
System.out.println(++ch); //Increment
}
}
Output:
64
B
]

[
Code:
import java.util.Scanner;
//Calculating CBSE board percentage
Scanner scan = new Scanner(System.in);
System.out.println("Enter your Physics marks: ");
int physics = scan.nextInt() ;//nextInt() is used for input
System.out.println("Enter your English marks: ");
int english = scan.nextInt();
System.out.println("Enter your Chemistry marks: ");
int chemistry = scan.nextInt();
System.out.println("Enter your Mathematics marks: ");
int mathematics = scan.nextInt();
System.out.println("Enter your computer science marks:");
int computer = scan.nextInt();
float r = ((physics + english+chemistry+mathematics+computer)/500.0f)*100;
System.out.println("Your Percentage is:");
System.out.println(r);
}
}
Output:
Enter your Physics marks:
95
Enter your English marks:
97
Enter your Chemistry marks:
84
Enter your Mathematics marks:
86
Enter your computer science marks:
92
Your Percentage is:
90.8
]

[
Code:
float a = 7/4.0f *9/2.0f ; // arithmetic between int and i t is int, to get
correct value convert to float
}
}
Output:
7.875
]
[
Code:
public class CWH_CH12_ps2_pr01 {
//Type casting used as (char) to convert (grade+8) which is int to char
char grade = 'B';
grade = (char)(grade+8); //In type casting no need to write type in start as
usual
System.out.println(grade);
grade = (char)(grade-8);
System.out.println(grade);
}
}
Output:
J
B
]

[
Code:
//To check if Given number is greater than user defined or not using user
defined functioned
System.out.println(a>8);
}
}
Output:
4
False
]
[
Code:
int v = sc.nextInt();
int u = sc.nextInt();
int s = sc.nextInt();
float r = (float)(v*v - u*u)/(2*a*s);
System.out.println(r);
}
}
Output:
2
3
4
5

-0.125
]
[
Code:
public class CWH_16_conditionals{
int age = 20;
if (age>18){
System.out.println("yes boy you can drive");
}
// else{
// System.out.println("No boy you cannot drive yet");
// }
}
}
Output:
yes boy you can drive
]
[
Code:
int age = 20;
if (age!=18){ //Using relational operators
System.out.println("yes boy you can drive");
}
else{
System.out.println("No boy you cannot drive yet");
}
}
}
Output:
yes boy you can drive
]

[
Code:
public class Main {
boolean a = true;
boolean b = false;
if (a&&b){
System.out.println("Y");
}
else{
System.out.println("N");
}
}
}
Output:
N
]
[
Code:
public class Main {
boolean a = true;
boolean b = false;
boolean c = true;
if (a&&b&&c){
System.out.println("Y");
}
else{
System.out.println("N");
}
}
}
Output:
N
]

[
Code:
int age;
age = sc.nextInt();
if (age>56){
System.out.println("You are experienced");
}
else if (age>46){
System.out.println("You are semi-experienced");
}
else if (age>36){
System.out.println("You are semi-semi-experienced");
}
else{
System.out.println("You are not experienced");
}
}
}
Output:
38
You are semi-semi-experienced
]
[
Code:
int age;
System.out.println("Enter age");
age = sc.nextInt();
switch(age){
case 18:
System.out.println("You are an Adult");
break;
case 20:

System.out.println("You are going to get a job");
break;
case 60:
System.out.println("You are going to get retired");
break;
default:
System.out.println("Enjoy your Life!");
}
}
}
Output:
Enter age
38
Enjoy your Life!
]
[
Code:
String var = "Harry";
switch(var){
case "Saurabh":
System.out.println("You are an Adult");
break;
case "Harry" :
System.out.println("You are going to get a job");
break;
case "Adhitya" :
System.out.println("You are going to get retired");
break;
default:
System.out.println("Enjoy your Life!");
}
}
}

Output:
You are going to get a job
]
[
Code:
String var = "Harry";
switch (var) {
case "Saurabh" -> System.out.println("You are an Adult"); //Enhanced
switch statement
case "Harry" -> System.out.println("You are going to get a job");
case "Adhitya" -> System.out.println("You are going to get retired");
default -> System.out.println("Enjoy your Life!");
}
}
}
Output:
You are going to get a job
]
[
Code:
int a = 10;
if (a==11){
System.out.println("I am 11");
}
else{
System.out.println("I am not 11");
}
}
}

Output:
I am not 11
]
[
Code:
//Find if a student is pass or fail
// use byte as number is below or equal to 100
byte m1,m2,m3;
System.out.println("Enter your marks in Physics");
m1 = sc.nextByte();
System.out.println("Enter your marks in Chemistry");
m2 = sc.nextByte();
System.out.println("Enter your marks in Mathematics");
m3 = sc.nextByte();
float avg = (m1+m2+m3)/3.0f;
if (avg>=40 && m1>=33 && m2>=33 && m3>=33){
System.out.println("Congrats, you are promoted");
}
else{
System.out.println("repeat the course");
}

}
}
Output:
Enter your marks in Physics
95
Enter your marks in Chemistry
84
Enter your marks in Mathematics
86
Congrats, you are promoted
]
[
Code:
//Problem- write java problem to find out the day of the week given number(1-
Monay, 2-Tuesday, etc.)
System.out.println("enter number of day: ");
int day = sc.nextInt();
switch(day){
case 1-> System.out.println("Monday");
case 2-> System.out.println("Tuesday");
case 3-> System.out.println("Wednesday");
case 4-> System.out.println("Thursday");
case 5-> System.out.println("Friday");
case 6-> System.out.println("Saturday");
case 7-> System.out.println("Sunday");
}
}
}

Output:
enter number of day:
2
Tuesday
]
[
Code:
//Problem - From URL from user find out what type of website it is
System.out.println("Enter URL");
String website = sc.nextLine();
if (website.endsWith(".org")){
System.out.println("Organizational website");
}
else if (website.endsWith(".com")){
System.out.println("Commercial website");
}
else if (website.endsWith(".in")){
System.out.println("Indian website");
}
}
}

Output:
Enter URL
https://www.youtube.com
Commercial website
]
[
Code:
int i = 1;
System.out.println("Using Loops: ");
while(i<=3){
i++;
}
System.out.println("Finished using Loops! ");
}
}
Output:
Using Loops:
1
2
3
Finished using Loops!
]

[
Code:
public class CWH_22_do_while {
int a =0;
while(a<5){
a++;
}
}
}
Output:
0
1
2
3
4
]
[
Code:
int b=10;
do{
System.out.println(b); //do-while loop executes first loop without
checking condition
b++;
}while(b<5);
}
}
Output:
10
]

[
Code:
int c =1;
do{
System.out.println(c);
c++;
}while(c<=45);
}
}
Output:
1
2
3
4
5
6
7
8
9
10

11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39

40
41
42
43
44
45
]
[
Code:
public class CWH_23_for_loop {
for (int i =1;i<=10; i++){
}
}
}
Output:
1
2
3
4
5
6
7
8
9
10
]

[
Code:
int n = 5;
for (int i = 0; i<=5; i++){
System.out.println(2*i+1);
}
}
}
Output:
1
3
5
7
9
11
]
[
Code:
for(int i =5; i!=0; i--){
}
}
}

Output:
5
4
3
2
1
]
[
Code:
//break and continue using loops
for (int i =0; i<5; i++){
System.out.println("Java is great");
if (i==2){
System.out.println("Ending the loop");
break;
}
}
}
}
Output:
0
Java is great
1
Java is great
2
Java is great
Ending the loop
]

[
Code:
public class CWH_24_break_and_continue {
//Practice Problem 1 - Create pattern of * using loop
int n =4;
for (int i=n; i>0; i--){
for (int j=0; j<i;j++){
System.out.print("*");
}
System.out.println("n");
}
}
}
Output:
****
***
**
*
]
[
Code:
//Practice Problem 2 - sum of first n even numbers
int sum=0;
int n=4;
for (int i=0;i<n;i++){
sum = sum + (2*i);
}
System.out.print("Sum of first %d even numbers ");
System.out.println(sum);
}
}

Output:
Sum of first %d even numbers 12
Process finished with exit code 0
]
[
Code:
//Problem - Write a program to print multiplication of a number n
int n=5;
for (int i=1; i<=10;i++){
System.out.printf("%d X %d = %d", n,i, n*i);
System.out.println("n");
}
}
}
Output:
5 X 1 = 5
5 X 2 = 10
5 X 3 = 15
5 X 4 = 20
5 X 5 = 25

5 X 6 = 30
5 X 7 = 35
5 X 8 = 40
5 X 9 = 45
5 X 10 = 50
]
[
Code:
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a number: ");
int number = scanner.nextInt();
scanner.close();
long factorial = 1;
for (int i = 1; i <= number; i++) {
factorial *= i;
}
System.out.println("Factorial of " + number + " is: " + factorial);
}
}
Output:
Enter a number: 6
Factorial of 6 is: 720
]

[
Code:
//Problem- Factorial using while loop
int n=5;
// what is factorial = n*n-1*n-2..1
int i =1;
//5!=5*4*3*2*1
int factorial =1;
while(i<=n){
factorial*=i;
i++;
}
System.out.println(factorial);
}
}
Output:
120
]
[
Code:
//print sum of the numbers in product side of multiplication table of 8
int n=8;
int sum=0;
for (int i=1; i<=10; i++){
sum+=n*i;
}
}
}
Output:
440
]

[
Code:
public class cwh_26_arrays {
//Classroom of 5 marks - you have to store marks of 500 students
//You have 2 options-
//1. create 5 variables
//2.Use arrays
//Array is a collection of similar types of data
// array format is [datatype[] arrayName]
int [] marks = new int[5];
marks[0]= 50;
marks[1]=70;
marks[2]=30;
marks[3]=86;
marks[4]=93;
System.out.println(marks[4]);
}
}
Output:
93
]
[
Code:
//Other ways of declaring arrays
//method -2
int []marks;
marks = new int[5];
//method -3
int [] list ={100,70,80,45,71};
System.out.println(list[2]);
}
}
Output:
80
]

[
Code:
int [] marks = {100,30,80,96,78};
System.out.println(marks.length);
float [] marks1 = {45.1f, 76.3f, 67.3f, 98.5f, 46};
System.out.println(marks1[4]);
String [] students = {"Harry", "Lovish", "Rohan", "Shubham"};
System.out.println(students.length);
}
}
Output:
96
5
46.0
4
]

[
Code:
int [] marks = {100,30,80,96,78};
System.out.println(marks.length);
float [] marks1 = {45.1f, 76.3f, 67.3f, 98.5f, 46};
System.out.println(marks1[4]);
String [] students = {"Harry", "Lovish", "Rohan", "Shubham"};
System.out.println(students.length);
//Displaying array
// Forward using for loop
for (int i=0; i<marks.length; i++){
}
// reverse using for loop
for (int i = marks.length -1; i>=0; i--){
}
//for each loop for displaying
System.out.println("Printing using for-each loop");
for (int element: marks){
System.out.println(element);
}
}
}
Output:
96
5
46.0
4
0
1
2
3
4
4

3
2
1
0
Printing using for-each loop
100
30
80
96
78
]
[
Code:
public class cwh_29_Practice_Set_6 {
//Problem - create an array of 5 floats and find their sum
float [] marks = {45.7f, 34.6f, 100.0f, 93.5f, 94.8f};
float sum =0;
for (float element : marks){
sum = sum+ element;
}
System.out.println("the value of sum is: ");
}
}
Output:
the value of sum is:
368.59998
]

[
Code:
//Problem - create an array of 5 floats and find their sum
float [] marks = {45.7f, 34.6f, 100.0f, 93.5f, 94.8f};
float num = 45.7f;
boolean isInArray= false;
for (float element : marks){
if (num==element){
isInArray=true;
break;
}
}
if (isInArray){
System.out.println("the value is present in the Array");
}
else{
System.out.println("the value is not present in the Array");
}
}
}
Output:
the value is present in the Array
]

[
Code:
//Problem - calculate average of marks of an array containing marks of all
students in physics
int [] marks = {34, 56, 78, 98, 100};
int sum = 0;
for (int i =0; i< marks.length; i++){
sum = sum + i;
}
int avg = sum/marks.length;
System.out.print("Average of the numbers in the array is ");
System.out.println(avg);
//Using for each loop
for (int element : marks){
sum = sum + element;
}
System.out.println("Average using for each loop is "+ sum/marks.length);
}
}
Output:
Average of the numbers in the array is 2
Average using for each loop is 75
]

[
Code:
//Problem - create a java program to add 2 matrices of size 2X3
// we will do it using arrays
int [][]mat1 = {{1,2,3},
{4,5,6}}; // as in 2-D arrays it is equivalent to [row][column]
int [][] mat2 = {{2,5,6},
{12, 43, 1}};
int [][] result ={{0,0,0},
{0,0,0}};
for (int i=0; i< mat1.length; i++){
for (int j=0; j< mat1[i].length; j++){
result[i][j] = mat1[i][j]+ mat2[i][j];
System.out.printf(result[i][j]+ " ");
}
System.out.print("n");
}
}
}
Output:
3 7 9
16 48 7
]
[
Code:
public class cwh_31_methods {
int a= 5;
int b=7;
int c= (a+b)*5;
}
}
Output:
60
]

[
Code:
int a= 5;
int b=7;
int c;
if (a>b){
c = a+b;
}
else{
c = (a+b)*5;
}
int a1=2;
int b1=1;
int c1;
if (a1>b1){
c1 =a1+b1;
}
else{
c1 = (a1+b1)*5;
}
System.out.println(c1);
}
}
Output:
60
3
]

[
Code:
//Java methods is equivalent to functions in Python
static int logic(int x, int y){
int z;
if (x>y){
z = x+y;
}
else{
z = (x+y)*5;
}
return z;
}
int a= 5;
int b=7;
int c;
c =logic(a,b);
int a1=2;
int b1=1;
int c1;
c1 = logic(a1, b1);
}
}
Output:
60
3
]

[
Code:
//Java method belongs to the class. Without static keyword, we have to make object and call
as shown
// only static methods can be called directly within public static void main(String[] args)
// Method invocation using object creation
int logic(int x, int y){
int z;
if (x>y){
z = x+y;
}
else{
z = (x+y)*5;
}
return z;
}
int a= 5;
int b=7;
int c;
cwh_31_methods obj = new cwh_31_methods();
c =obj.logic(a,b);
int a1=2;
int b1=1;
int c1;
c1 = obj.logic(a1, b1);
}
}
Output:
60
3
]
[
Code:
public class cwh_32_method_overloading {
static void tellJoke(){
System.out.println("I invented a new word n" +
"Plagiarism!");
}
tellJoke();
}
}

Output:
I invented a new word
Plagiarism!
]
[
Code:
static void change(int a){
a = 98;
}
int x = 45;
change(x); //copy of x's value goes to method change and hence actual value of x doesnt
change
System.out.println( "the value of x after change method is "+ x);
}
}
Output:
the value of x after change method is 45
]
[
Code:
static void change(int a){
a = 98;
}
static void change2(int [] arr){
arr[0]= 98;
}
// Case 1 - Changing the integer
//int x = 45;
// change(x); //copy of x's value goes to method change and hence actual value of x
doesnt change
// System.out.println( "the value of x after change method is "+ x);
// value of x didn't change. It will change only if reference is passed and not the copy
of the object
//Case 2- Changing the Array
int [] marks = {52, 76, 98, 56, 78, 93};
change2(marks); // marks is reference. As reference is passed into change2,
// arr and marks refer to the same array and marks[0] value changes
System.out.println("the first value of array after change2 "+ marks[0]);
}
}

Output:
the first value of array after change2 98
]
[
Code:
//Method Overloading - same name methods with different parameters
static void foo(){
System.out.println("Good morning Bro! ");
}
static void foo(int a){
System.out.println("Good morning "+ a + " Bro!");
}
foo();
foo(34);
} // a is parameter while 34 is argument
}//Arguments are actual!
//Cannot do overloading by changing return type. Void is return type, int is return type.
//Both void and int return types are written beside static
Output:
Good morning Bro!
Good morning 34 Bro!
]

[
Code:
public class cwh_33_varargs {
static int sum(int a, int b){
return a+b;
}
static int sum(int a, int b,int c){
return a+b+c;
}
// Varargs method to replace all the above methods
static int sum(int ...arr){
// Available as int [] arr
int result = 0;
for (int a : arr){
result+=a;
}
return result;
}
System.out.println("Welcome to Varargs Tutorial");
System.out.println("Sum of 4 and 5 is "+ sum(4,5));
System.out.println("Sum of 4 and 5 is "+ sum(4,3,5));
// further if we want to get sum for n numbers we cannot keep doing overloading
// to solve this we use varargs
System.out.println("Sum of Random number of numbers by varargs is "+
sum(4,5,6,7,8,9,2,122,2332));
}
}
Output:
Welcome to Varargs Tutorial
Sum of 4 and 5 is 9
Sum of 4 and 5 is 12
Sum of Random number of numbers by varargs is 2495
]

[
Code:
public class cwh_33_varargs {
static int sum(int a, int b){
return a+b;
}
static int sum(int a, int b,int c){
return a+b+c;
}
// Varargs method to replace all the above methods
static int sum(int x, int ...arr){
// Available as int [] arr
int result = x;
for (int a : arr){
result+=a;
}
return result;
}
System.out.println("Welcome to Varargs Tutorial");
System.out.println("Sum of 4 and 5 is "+ sum(4,5));
System.out.println("Sum of 4 and 5 is "+ sum(4,3,5));
// further if we want to get sum for n numbers we cannot keep doing overloading
// to solve this we use varargs
System.out.println("Sum of Random number of numbers by varargs is "+
sum(4,5,6,7,8,9,2,122,2332));
}
}
Output:
Welcome to Varargs Tutorial
Sum of 4 and 5 is 9
Sum of 4 and 5 is 12
Sum of Random number of numbers by varargs is 2495
]

[
Code:
//Recursion is when the function/method calls itself when it is executed
//factorial can be done using recursion
public class cwh_34_recursion {
static int factorial(int n){
if (n==0 || n==1){
return 1;
}
else{
return n* factorial(n-1);
}
}
int n=4;
System.out.println("Factorial of 4 is "+ factorial(n));
}
}
Output:
Factorial of 4 is 24
]
[
Code:
//Problem- multiplication of a number using Java methods
static void multiplication(int n){
for (int i =0; i<=10; i++){
System.out.printf("%d X %d = %dn", n, i, n*i);
}
}
multiplication(7);
}
}
Output:
7 X 0 = 0
7 X 1 = 7
7 X 2 = 14
7 X 3 = 21

7 X 4 = 28
7 X 5 = 35
7 X 6 = 42
7 X 7 = 49
7 X 8 = 56
7 X 9 = 63
7 X 10 = 70
]
[
Code:
//Problem- Create desired pattern using Java methods
static void star(int n){
for (int i=1; i<=n; i++){
for (int j=0; j<i; j++){
}
System.out.println();
}
}
star(4);
}
}
Output:
*
**
***
****
]

[
Code:
//Problem-write a recursive function to find sum of first n natural numbers
static int sumRec(int n){
if (n==1){
return 1;
}
else{
return n+ sumRec(n-1);
}
}
int c = sumRec(4);
System.out.print("Sum of n natural numbers using recursion function is ");
}
}
Output:
Sum of n natural numbers using recursion function is 10
]
[
Code:
//Problem- Create desired pattern using Java methods
static void star(int n){
for (int i=1; i<=n; i++){
for (int j=n; j>i -1; j--){
}
System.out.println();
}
}
star(4);
}
}

Output:
****
***
**
*
]
[
Code:
//Problem- write a function to print nth term of the fibonnaci series using recursion
// fibonacci series - 0,1,1,2,3,5,8,13,21,34,...
static int fib(int n){
if (n==1){
return 0;
}
else if (n==2){
return 1;
}
else{
return fib(n-1)+fib(n-2);
}
}
int c = fib(8);
System.out.print("nth term of the Fibonacci series is ");
}
}
Output:
nth term of the Fibonacci series is 13
]

[
Code:
//custom class has attributes within it
//there can be only one 1 public class in 1 java file
class Employee{
int id;
int salary;
String name;
//String data type has S capital
//Just as methpd/function has parameters, Java class has attrubutes to create objects with
new keyword
public void printDetails(){
System.out.println("My id is "+ id);
System.out.println("My name is "+ name);
}
public int getSalary(){
return salary;
}
}
public class cwh_38_custom_class {
System.out.println("This is our First Custom Class");
//Setting attributes
Employee harry = new Employee();
harry.id = 12;
harry.name = "CodeWithHarry";
harry.salary = 12;
Employee Adhitya = new Employee();
Adhitya.id = 1;
Adhitya.name = "M Adhitya";
Adhitya.salary = 100;
//Any real world object = properties + Behavior; similarly
//objects in OOPs = attributes + methods
//Printing the properties/attributes-
System.out.println("Adhitya's id- ");
System.out.print(Adhitya.id);
System.out.println("Adhitya's full name- ");
System.out.println(Adhitya.name);
//Instead of again and again writing like above, we would like to call a method
System.out.println("Adhitya's details using custom method in custom class- ");
Adhitya.printDetails();// as sout in printDetails already, dont write
Adhitya.printDetails() withing sout here
System.out.println(harry.getSalary());
System.out.println(Adhitya.getSalary());
}
}

Output:
This is our First Custom Class
Adhitya's id-
1Adhitya's full name-
M Adhitya
Adhitya's details using custom method in custom class-
My id is 1
My name is M Adhitya
12
100
]
[
Code:
//Problem - Create Employee1 custom class
class Employee1 {
int salary;
String name;
public int getSalary() {
return salary;
}
public String getName() {
return name;
}
public void setName(String n) {
name = n;
}
}
public class cwh_39_ch8_ps {
Employee1 Harry = new Employee1();
Harry.setName("Adhitya");
Harry.salary = 123;
System.out.println(Harry.getName());
System.out.println(Harry.getSalary());
}
}

Output:
Adhitya
123
]
[
Code:
//Problem - Create class CellPhone which prints ringing.. vibrating.. etc.
class CellPhone{
public void ring(){
System.out.println("Ringing...");
}
public void vibrate(){
System.out.println("Vibrating...");
}
public void callFriend (){
System.out.println("calling Aaditya Aryan");
}
}
CellPhone samsung = new CellPhone();
samsung.callFriend();
samsung.ring();
samsung.vibrate();
}
}
Output:
calling Aaditya Aryan
Ringing...
Vibrating...
]

[
Code:
//Problem- create class square with a initialize its side, calculating area, perimeter, etc
class Square{
int side;
public float area(){
return side*side;
}
public int perimeter(){
return 4*side;
}
}
Square a = new Square();
a.side = 4;
System.out.println(a.area());
System.out.println(a.perimeter());
}
}
Output:
16.0
16
]
[
Code:
//Problem- create class Tommy capable of hitting, firing, running, etc.
class Tommy{
public void hit(){
System.out.println("Hitting the enemy");
}
public void run(){
System.out.println("Running from Enemy");
}
public void fire(){
System.out.println("Firing the enemy");
}
}
Tommy player1 = new Tommy();
player1.hit();
player1.run();
player1.fire();
}
}

Output:
Hitting the enemy
Running from Enemy
Firing the enemy
]
[
Code:
class MyEmployee{
private int id;
private String name;
public void setName(String n){
this.name = n;
}
public String getName(){
return name;
}
public void setId(int i){
this.id = i; //this and other keywords here are access modifiers, getters & setters.
}
public int getId(){
return id;
}
}
public class cwh_40_ch9 {
MyEmployee Adhitya = new MyEmployee();
// Adhitya.id = 45;
// Adhitya.name = "Adhi; --> throws an error due to private access modifier
Adhitya.setName("Adhitya");
System.out.println("Adhitya's id after changing is - "+ Adhitya.getId());
System.out.println(Adhitya.getName());
}
}
Output:
Adhitya's id after changing is - 0
Adhitya
]

[
Code:
import java.util.Random;
//Rock Paper Scissor Game
public class cwh_ex2_soln {
// 0 for Rock
//1 for Paper
// 2 for Scissor
int userInput = sc.nextInt();
Random random = new Random();
int computerInput = random.nextInt();
if (userInput==computerInput){
System.out.println("Draw");
}
else if ((userInput==0 && computerInput ==2) || (userInput==1 &&computerInput==0) ||
(userInput ==2 && computerInput==1)){
System.out.println("You Win!");
}
else{
System.out.println("Computer Wins");
}
}
}
Output:
1
Computer Wins
]

[
Code:
//Problem - create a class cylinder and use getters and setters to set its radius and height
class Cylinder{
private int radius;
private int height;
//Click the three dots above and choose "code" then click "Generate" then use it to
//generate code like getter and setters - short trick
public int getHeight() {
return height;
}
public void setHeight(int height) {
this.height = height;
}
public int getRadius() {
return radius;
}
public void setRadius(int radius) {
this.radius = radius;
}
}
public class cwh_44_ps09 {
Cylinder myCylinder = new Cylinder();
myCylinder.setHeight(13);
int h = myCylinder.getHeight();
System.out.println(h);
myCylinder.setRadius(3);
System.out.println(myCylinder.getRadius());
}
}
Output:
13
3
]

[
Code:
//Problem - create a class cylinder and use getters and setters to set its radius and height
//with surface area and volume
class Cylinder{
private int radius;
private int height;
return height;
}
}
return radius;
}
}
public double surfaceArea(){
return 2*3.14*radius*radius + 2*3.14*radius*height;
}
public double volume(){
return 3.14*radius*radius*height;
}
}
Cylinder myCylinder = new Cylinder();
myCylinder.setHeight(13);
myCylinder.setRadius(3);
System.out.println(myCylinder.volume());
System.out.println(myCylinder.surfaceArea());
}
}
Output:
13
3
367.38
301.44
]

[
Code:
//Problem - create a class cylinder and use constructors to set its radius and height
//with surface area and volume
class Cylinder{
private int radius;
private int height;
public Cylinder(int radius, int height) {
this.height = height; //Using Constructor
}
return height;
}
}
return radius;
}
}
public double surfaceArea(){
return 2*Math.PI*radius*radius + 2*3.14*radius*height;
}
return Math.PI*radius*radius*height; //use Math.PI for accurate value of Pi
}
}
Cylinder myCylinder = new Cylinder(12,9);
// myCylinder.setHeight(13);
// myCylinder.setRadius(3);
System.out.println(myCylinder.volume());
System.out.println(myCylinder.surfaceArea());
}
}

Output:
9
12
4071.5040790523717
1583.0186842338603
]
[
Code:
//Problem - overload a constructor used to initialize a rectangle of length 4 and breadth 5
// for using custom parameters
class Rectangle {
private int length;
private int breadth;
public Rectangle(int length, int breadth) {
this.length = length;
this.breadth = breadth;
}
public int getLength() {
return length;
}
public void setLength(int length) {
this.length = length;
}
public int getBreadth() {
return breadth;
}
public void setBreadth(int breadth) {
this.breadth = breadth;
}
}
Rectangle r = new Rectangle(4,5);
System.out.println(r.getBreadth());
System.out.println(r.getLength());
}
}

Output:
5
4
]
[
Code:
//Problem - create a class Sphere and use getters and setters to print its surface area and
volume
class Sphere{
private int radius;
public void setRadius(int r){
radius = r;
}
public int getRadius(){
return radius;
}
public float area(){
return (float) (4*Math.PI*radius*radius);
}
return (4/3)*Math.PI*radius*radius*radius;
}
}
Sphere s = new Sphere();
s.setRadius(5);
System.out.println(s.getRadius());
System.out.println(s.area());
System.out.println(s.volume());
}
}
Output:
5
314.15927
392.69908169872417
]

[
Code:
//Inheritance concept
class Base{
int x;
public int getX() {
return x;
}
public void setX(int x) {
System.out.println("I am in base and I am setting value of X now");
this.x = x;
}
public void printMe(){
System.out.println("I am a constructor");
}
}
//Inheritance uses existing class to create new class in such a way,
// such that the code of previous class is also there behind the screen in current class
class Derived extends Base{
int y;
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
}
public class cwh_45_inheritance {
//Creating an object of base class
Base b = new Base();
b.setX(23);
System.out.println(b.getX());
//Creating an object of derived class in inheritance
Derived d = new Derived();
d.setX(23);
System.out.println(d.getX());
}
}
Output:
I am in base and I am setting value of X now
23
I am in base and I am setting value of X now
23
]

[
Code:
class Base1 {
Base1() { //Constructor is exact copypaste of method, just that its name is same as that of
class
System.out.println("I am a Constructor");
}
Base1(float x) {
System.out.println("I am an Overloaded Constructor with a value of " + x);
}
}
class Derived1 extends Base1 {
Derived1() {
super(0); //To use an argumented Constructed in derived class we use super keyword
System.out.println("I am derived class constructor");
}
}
public class cwh_46_constructors_in_inheritance {
Derived1 d = new Derived1();
}
}
Output:
I am an Overloaded Constructor with a value of 0.0
I am derived class constructor
]

[
Code:
class Base1 {
class
}
Base1(float x) {
}
}
Derived1() {
}
Derived1(int x, int y){
super(x);
System.out.println("I am an Overloaded Constructor with a value of " + y);
}
}
//Derived1 d = new Derived1();
Derived1 d = new Derived1(4,9);
}
}
Output:
I am an Overloaded Constructor with a value of 4.0
I am an Overloaded Constructor with a value of 9
]

[
Code:
class Base1 {
class
}
Base1(int x) {
}
}
Derived1() {
}
Derived1(int x, int y){
super(x);
System.out.println("I am an Overloaded Constructor with a value of " + y);
}
}
class ChildOfDerived1 extends Derived1{
ChildOfDerived1(){
System.out.println("I am a child of derived");
}
ChildOfDerived1(int x, int y, int z){
super(x, y);
System.out.println("I am an overloaded constructor of child of derived with value of z
as "+ z);
}
}
//Derived1 d = new Derived1();
// Derived1 d = new Derived1(4,9);
ChildOfDerived1 t = new ChildOfDerived1(3,4,5);
}
}
Output:
I am an overloaded constructor of child of derived with value of z as 5
]

[
Code:
import javax.print.Doc;
class EkClass {
int a;
public int getA() {
return a;
}
EkClass(int v) {
this.a = v;
}
public int returnone(){
return 1;
}
}
//super keyword is used to refer to the super class of the current class, and run the
constructor with arguments
class DoC extends EkClass{
DoC(int c){
super(c);
System.out.println("Mai ek constructor hun");
}
}
public class cwh_47_this_super {
EkClass e = new EkClass(65);
DoC d = new DoC(5);
System.out.println(e.getA());
}
}
Output:
Mai ek constructor hun
65
]

[
Code:
//method overriding
class A{
public int a;
public int harry(){
return 4;
}
public void meth2(){
System.out.println("I am method 2 of class A");
}
}
class B extends A{
System.out.println("I am method 2 of class B"); //This is method overriding
}// same meth2() of class A in class B so it implements its own meth2()
System.out.println("I am method 3 of class B");
}
}
public class cwh_48_method_overriding {
A a = new A();
a.meth2();
B b = new B();
b.meth2();
}
}
Output:
I am method 2 of class A
I am method 2 of class B
]

[
Code:
class Phone{
public void greet(){
System.out.println("Good Morning");
}
public void on(){
System.out.println("Turning on Phone");
}
}
class SmartPhone extends Phone{
public void swagat(){
System.out.println("Aapka swagat hai");
}
@Override
public void on(){
System.out.println("Turning on SmartPhone");
}
}
public class cwh_49_dynamic_method_dispatch {
Phone obj = new SmartPhone();//Superclass reference obj can be equal to sub class object
as here
//SmartPhone obj = new Phone(); // will give error, opposite is not allowed
obj.greet();
obj.on();// It exectutes of the object(smartphone) not of reference(phone)
//This is called dynamic method dispatching
}
}
Output:
Good Morning
Turning on SmartPhone
]

[
Code:
class Phone{
public void showTime(){
System.out.println("Time is 8 am");
}
public void on(){
System.out.println("Turning on Phone");
}
}
class SmartPhone extends Phone{
public void music(){
System.out.println("Playing music...");
}
@Override
public void on(){
System.out.println("Turning on SmartPhone");
}
}
public class cwh_49_dynamic_method_dispatch {
Phone obj = new SmartPhone();//Superclass reference obj can be equal to sub class object
as here
//SmartPhone obj = new Phone(); // will give error, opposite is not allowed
obj.showTime();
obj.on();// It exectutes of the object(smartphone) not of reference(phone)
//This is called dynamic method dispatching
//obj.music(); // is not allowed
}
}
Output:
Time is 8 am
Turning on SmartPhone
]

[
Code:
import java.util.Random;
class Game{
public int number;
public int inputNumber;
public int noOfGuesses;
public int getNoOfGuesses() {
return noOfGuesses;
}
public void setNoOfGuesses(int noOfGuesses) {
this.noOfGuesses = noOfGuesses;
}
Game(){
Random rand = new Random();
this.number = rand.nextInt(100);
}
void takeUserInput(){
System.out.println("Guess the number");
inputNumber= sc.nextInt();
}
boolean isCorrectNumber(){
if(inputNumber == number){
return true;
}
else if(inputNumber < number){
System.out.println("Too low...");
}
else if(inputNumber> number){
System.out.println("Too high...");
}
return false;
}
}
public class cwh_43_exercise3 {
/* create a class Game which allows user to play "Guess the Number"
game once.Game should have the following methods-
1. Constructor to generate the random number
2. takeUserInput() to take user input of a number
3. isCorrectNumber() i=to check whether entered number is correct
4. getter and setters for no. of guesses
Use properties such as noOfGuesses(int) to get the task done */
Game g = new Game();
boolean b = false;
while(!b) {
g.takeUserInput();
b = g.isCorrectNumber();
}
}
}

Output:
Guess the number
2
Too low...
false
Guess the number
5
Too low...
false
Guess the number
8
True
]

[
Code:
//create a class circle and use inheritance to create another class cylinder from it
class Circle{
Circle(){
System.out.println("I am non parameter of circle");
}
Circle(int r){
System.out.println("I am Circle Parameterized constructor");
this.radius = r;
}
public int radius;
public double area(){
return Math.PI*this.radius*this.radius;
}
}
class Cylinder extends Circle{
public int height;
Cylinder(int r, int h) {
//Super keyword means only super's words will be listened to first, so the
//default constructor will not be run, what super says will be run first
super(r);
System.out.println("I am Cylinder Parameterized constructor");
this.height=h;
}
return Math.PI*this.radius*this.radius*this.height;
}
}
public class cwh_52_chap10ps {
Circle obj = new Circle(12);
System.out.println("Area is: ");
System.out.println(obj.area());
Cylinder obj2 = new Cylinder(2,3);
System.out.println("Volume is: ");
System.out.println(obj2.volume());
}
}
Output:
I am Circle Parameterized constructor
Area is:
452.3893421169302
I am Circle Parameterized constructor
I am Cylinder Parameterized constructor
Volume is:
37.69911184307752
]

[
Code:
//Abstract class is a class jiski sahayata lekar aur classes aap bana te ho
//Abstract class ek class hota nhi hai, lekin vo ek zariya hai, Child2 jaise concrete class
banane ka
// Abstract classes cant have objects
//Analogy - Parent2 class is saying to his Child2 and Child3 classes, bacchon, please use
greet() abstract
//anyway you want or you yourself become a standard that is parent
abstract class Parent2{ // 1 abstract method makes whole class abstract.
//Must declare the whole class as abstract using abstract keyword
public Parent2(){
System.out.println("Mai base2 ka constructor hun");
}
public void sayHello(){
System.out.println("Hello");
}
abstract public void greet();
abstract public void greet2();
}
class Child2 extends Parent2{
@Override
public void greet(){
}
@Override
public void greet2(){
System.out.println("Good Afternoon");
}
}
abstract class Child3 extends Parent2{
public void th(){
System.out.println("I am Good");
}
}
public class cwh_53_abstract {
Child2 c = new Child2();
// Parent2 p = new Parent2(); ---- Error
// Child3 c3 = new Child3(); ---- Error
}
}
Output:
Mai base2 ka constructor hun
]

[
Code:
interface Bicycle{
int a = 45; // Attribute or property
void applyBrake(int decrement);
void speedUp(int increment);
}
interface HornBicycle{
public int b = 45;
void blowHornK3g();
void blowHornmhn();
}
class AvonCycle implements Bicycle,HornBicycle{
public int b = 5;
void blowHorn(){
System.out.println("Pee pee poo poo");
}
//ALWAYS the methods of interface should have public access modifiers
public void applyBrake(int decrement){
System.out.println("Applying brake...");
}
public void speedUp(int increment){
System.out.println("Speeding Up...");
}
public void blowHornK3g(){
System.out.println("Kabhi kushi kabhi gum pee pee pee pee");
}
public void blowHornmhn(){
System.out.println("Mai hun na po po po po");
}
}
public class cwh_54_Interfaces {
AvonCycle cycleAdhi = new AvonCycle();
cycleAdhi.applyBrake(1);
//You can create property in Interfaces
System.out.println(cycleAdhi.a);
//You can not modify the properties in Interfaces as they are final
// cycleAdhi.a = 454; ---> gives error
cycleAdhi.blowHornK3g();
cycleAdhi.blowHornmhn();
System.out.println(cycleAdhi.b);
}
}
Output:
Applying brake...
45
Kabhi kushi kabhi gum pee pee pee pee
Mai hun na po po po po
5
]

[
Code:
interface MyCamera {
void takeSnap();
void recordVideo();
private void greet(){
}
default void record4KVideo() {
greet(); // private methods in interface cannot be directly used by class but, using
default methods
// we can use the private method
System.out.println("Recording 4K...");
} //default was introduced as if we add 1 abstract method in interface, all existin classes
implementing
//the interface will fail, and we have to correct all of them, so we add
//default method so that we dont need to edit ALL existing classes using the interface
}
interface MyWifi{
String [] getNetworks();
void connectToNetwork(String network);
}
class MyCellPhone{
void callnumber(int phoneNumber){
System.out.println("Calling"+ phoneNumber);
}
void pickCall(){
System.out.println("Connecting...");
}
public void takeSnap(){
System.out.println("Taking snap");
}
}
class MySmartPhone extends MyCellPhone implements MyWifi, MyCamera{
}
public void recordVideo(){
}
@Override
public void record4KVideo(){
System.out.println("Taking Snap and recording 4K Video"); // can comment this override
code to get another output
}
public String [] getNetworks() {
System.out.println("Getting List of Networks");
String [] networkList = {"Adhi", "Jake"};
return networkList;
}
public void connectToNetwork(String network){
System.out.println("Connecting.."+ network);
}
}
public class cwh_57_default_methods {
MySmartPhone ms = new MySmartPhone();

ms.record4KVideo(); //Default method
String [] ar = ms.getNetworks();
for (String item : ar){
System.out.println(item);
}
}
}
//Two types of methods - static methods and default methods
// Static method is not associated with object, it is only associated with class or interface
Output:
Taking Snap and recording 4K Video
Getting List of Networks
Adhi
Jake
]
[
Code:
//To follow the Do Not Repeat Yourself(DRY) principle, we follow Inheritance in Interfaces
interface sampleInterface{
void meth1();
void meth2();
}
interface childSampleInterface extends sampleInterface{
void meth3();
void meth4();
}
class MySampleClass implements childSampleInterface{
System.out.println("meth1");
}
}
}
}
}
public class cwh_58_inheritance_interfaces {
MySampleClass obj = new MySampleClass();
obj.meth1();
obj.meth2();
obj.meth3();
obj.meth4();
}
}

Output:
meth1
meth2
meth3
meth4
]
[
Code:
//Polymorphism
interface MyCamera2{
void takeSnap();
void recordVideo();
private void greet(){
}
default void record4KVideo() {
greet(); // private methods in interface cannot be directly used by class but, using
default methods
// we can use the private method
System.out.println("Recording 4K...");
} //default was introduced as if we add 1 abstract method in interface, all existin classes
implementing
//the interface will fail, and we have to correct all of them, so we add
//default method so that we dont need to edit ALL existing classes using the interface
}
interface MyWifi2{
String [] getNetworks();
void connectToNetwork(String network);
}
class MyCellPhone2{
void callnumber(int phoneNumber){
System.out.println("Calling"+ phoneNumber);
}
void pickCall(){
System.out.println("Connecting...");
}
}
}
class MySmartPhone2 extends MyCellPhone2 implements MyWifi2, MyCamera2{
}
public void recordVideo(){
}
@Override
public void record4KVideo(){
System.out.println("Taking Snap and recording 4K Video"); // can comment this override
code to get another output

}
public String [] getNetworks() {
System.out.println("Getting List of Networks");
String [] networkList = {"Adhi", "Jake"};
return networkList;
}
public void connectToNetwork(String network){
System.out.println("Connecting.."+ network);
}
}
public class cwh_59_polymorphism {
MyCamera2 cam1 = new MySmartPhone2(); //This is a SmartPhone but use it as a Camera
//cam1.getNetworks(); ----> not allowed
cam1.record4KVideo();
MySmartPhone2 s = new MySmartPhone2();
s.getNetworks();
s.recordVideo();
s.callnumber(23453);
}
}
Output:
Taking Snap and recording 4K Video
Getting List of Networks
Taking snap
Calling23453
]

[
Code:
//create an abstract class Pen with abstract methods write() and refill() as abstract methods
//create a concrete class FountainPen with additional method changeNib()
abstract class Pen{
abstract void write();
abstract void refill();
}
class FountainPen extends Pen{
void write(){
System.out.println("Writing");
}
void refill(){
System.out.println("Refill");
}
void changeNib(){
System.out.println("Changing the Nib");
}
}
public class cwh_60_ch11ps {
FountainPen pen = new FountainPen();
pen.changeNib();
}
}
Output:
Changing the Nib
]

[
Code:
//create class Monkey with jump() and bite() methods. Create a class Human which inherits this
class Monkey
//and implements BasicAnimal interface with eat() and sleep() methods
class Monkey{
void jump(){
System.out.println("Jumping...");
}
void bite(){
System.out.println("Biting...");
}
}
interface BasicAnimal{
void eat();
void sleep();
}
class Human extends Monkey implements BasicAnimal{
void speak(){
System.out.println("Hello !");
}
public void eat(){
System.out.println("Eating...");
}
public void sleep(){
System.out.println("Sleeping...");
}
}
Human Adhi = new Human();
Adhi.eat();
Adhi.sleep();
Adhi.speak();
Adhi.bite();
Adhi.jump();
}
}
Output:
Eating...
Sleeping...
Hello !
Biting...
Jumping...
]

[
Code:
//create class Monkey with jump() and bite() methods. Create a class Human which inherits this
class Monkey
//and implements BasicAnimal interface with eat() and sleep() methods
// And demonstrate polymorphism
class Monkey{
void jump(){
System.out.println("Jumping...");
}
void bite(){
System.out.println("Biting...");
}
}
interface BasicAnimal{
void eat();
void sleep();
}
class Human extends Monkey implements BasicAnimal{
void speak(){
System.out.println("Hello !");
}
public void eat(){
System.out.println("Eating...");
}
public void sleep(){
System.out.println("Sleeping...");
}
}
Human Adhi = new Human();
Adhi.eat();
Adhi.sleep();
Adhi.speak();
Adhi.bite();
Adhi.jump();
Monkey m1 = new Human();
// m1.speak(); // ---> gives error, cannot use speak() method as
// reference is Monkey which does not have speak() method
m1.jump();
m1.bite();
BasicAnimal lovish = new Human();
//lovish.speak(); ---> gives error and this demonstrates polymorphism
}
}

Output:
Eating...
Sleeping...
Hello !
Biting...
Jumping...
Jumping...
Biting...
]

[
Code:
class Library{
String []books;
int no_of_books = 0;
Library(){
this.books = new String[100];
this.no_of_books=0;
}
void addBook(String book){
this.books[no_of_books]= book;
no_of_books++;
System.out.println(book + " has been added!");
}
void showAvailableBooks(){
System.out.println("Available Books are...");
for(String item : this.books){
if(item == null){
continue;
}
System.out.println("*" + item);
}
}
void issueBook(String book){
for (int i =0; i<this.books.length; i++){
if(this.books[i].equals(book)){
System.out.println("This book has been issued!");
this.books[i]= null;
return;
}
}
System.out.println("This book does not exist!");
}
void returnBook(String book){
addBook(book);
}
}
public class cwh_51_exercise4 {
//You have to implement a class library using Java Class Library
//Methods: issueBook, returnBook, showAvailableBooks
//Properties: array to store the available books
//Array to store issued books
Library centralLibrary = new Library();
centralLibrary.addBook("Think and Grow Rich!");
centralLibrary.addBook("Ikigai");
centralLibrary.addBook("Atomic Habits");
centralLibrary.showAvailableBooks();
centralLibrary.issueBook("Atomic Habits");
centralLibrary.showAvailableBooks();;
centralLibrary.returnBook("Atomic Habits");
centralLibrary.showAvailableBooks();
}
}

Output:
Think and Grow Rich! has been added!
Ikigai has been added!
Atomic Habits has been added!
Available Books are...
*Think and Grow Rich!
*Ikigai
*Atomic Habits
This book has been issued!
*Ikigai
Atomic Habits has been added!
*Ikigai
*Atomic Habits
]

[
Code:
//Access modifiers access in same class illustration
class C1{
public int x = 5;
protected int y = 45;
int z = 7;
private int a = 73;
System.out.println(x);
System.out.println(y);
System.out.println(z);
}
}
public class cwh_66_access_modifiers {
C1 c = new C1();
c.meth1();
}
}
Output:
5
45
7
73
]

[
Code:
//Access modifiers access in same package illustration
class C1{
public int x = 5;
protected int y = 45;
int z = 7;
private int a = 73;
System.out.println(x);
System.out.println(y);
System.out.println(z);
}
}
public class cwh_66_access_modifiers {
C1 c = new C1();
System.out.println(c.x);
System.out.println(c.y);
System.out.println(c.z);
//System.out.println(c.a); --> gives error as private access
}
}
Output:
5
45
7
]

[
Code:
//Difference b/w concurrency and parallelism is similar to difference b/w parameters and
arguments
// Concurrency means, you are managing multiple tasks overall, but at a time you are doing only
one task
//Parallelism means actually both tasks are happening together simultaneously
//Multithreading in java follows concurrency
//We use Threads to achieve multitasking within a process
class MyThread1 extends Thread{
@Override
public void run(){
int i = 0;
while(i<5){
System.out.println("My thread is running");
System.out.println("I am happy!");
i++;
}
}
}
class MyThread2 extends Thread{
@Override
public void run(){
int i = 0;
while(i<5){
System.out.println("Thread2 is good");
System.out.println("I am sad");
i++;
}
}
}
public class cwh_70 {
MyThread1 t1 = new MyThread1();
MyThread2 t2 = new MyThread2();
t1.start();
t2.start();// start() is method to run threads
}
}

Output:
My thread is running
Thread2 is good
I am happy!
I am happy!
I am happy!
I am happy!
I am happy!
I am sad
Thread2 is good
I am sad
Thread2 is good
I am sad
Thread2 is good
I am sad
Thread2 is good
I am sad
]

[
Code:
//Runnable is an in built interface in Thread
class MyThreadRunnable1 implements Runnable{
public void run(){
System.out.println("I am a thread1 not a threat1");
}
}
class MyThreadRunnable2 implements Runnable{
public void run(){
System.out.println("I am a thread2 not a threat2");
}
}
public class cwh_71_runnable {
MyThreadRunnable1 bullet1 = new MyThreadRunnable1();
MyThreadRunnable2 bullet2 = new MyThreadRunnable2();
Thread gun1 = new Thread(bullet1);
Thread gun2 = new Thread(bullet2);
gun1.start();
gun2.start();
}
}
Output:
I am a thread1 not a threat1
I am a thread2 not a threat2
]

[
Code:
//Thread is a class
//Refer to notes for Constructors in java types
//start() is for starting Thread
class MyThr extends Thread{
public MyThr(String name){
super(name); // as there is already a constructor in Thread that uses name
}
public void run(){
int i = 34;
System.out.println("Thank you");
}
}
public class cwh_73_thread_constructor {
MyThr t = new MyThr("Adhi");
MyThr t2 = new MyThr("M");
t.start();
System.out.println("The id of this thread is "+ t.getId());
System.out.println("The name of the thread is "+ t.getName());
System.out.println("The id of t2 is "+ t.getId());
System.out.println("The name of t2 is "+ t.getName());
}
}
Output:
The id of this thread is 20
The name of the thread is Adhi
The id of t2 is 20
The name of t2 is Adhi
Thank you
]

[
Code:
class MyThr1 extends Thread{
public MyThr1(String name){
}
public void run(){
int i = 34;
System.out.println("Thank you " + this.getName());
}
}
public class cwh_74_thread_priorities {
MyThr1 t1 = new MyThr1("Adhi1");
t1.start();
t2.start();
t3.start();
t4.start();
t5.start();
}
}
Output:
Thank you Adhi1
Thank you Adhi2
Thank you Adhi3
Thank you Adhi4
Thank you Adhi5
]

[
Code:
//Thread Priorities
class MyThr1 extends Thread{
public MyThr1(String name){
}
public void run(){
int i = 34;
System.out.println("Thank you " + this.getName());
}
}
public class cwh_74_thread_priorities {
t5.setPriority(Thread.MAX_PRIORITY); //max priority
t1.setPriority(Thread.MIN_PRIORITY); //min priority
t1.start();
t2.start();
t3.start();
t4.start();
t5.start();
}
}
Output:
Thank you Adhi5
Thank you Adhi2
Thank you Adhi3
Thank you Adhi4
Thank you Adhi1
]

[
Code:
class MyNewThr1 extends Thread{
public void run(){
int i = 0;
while(i<8){
i++;
}
}
}
public void run(){
int j = 0;
while(j<8){
System.out.println("Thank you2");
j++;
}
}
}
public class cwh_75_thread_method {
MyNewThr1 t1 = new MyNewThr1();
t1.start();
try{ //put it in try-catch block
t1.join(); //Join can be used if you want it like till t1 doesnt end, t2 doesnt
start
}
catch(Exception e){
System.out.println(e);
}
t2.start();
}
}
Output:
Thank you
Thank you
Thank you
Thank you
Thank you
Thank you
Thank you
Thank you
Thank you2

Thank you2
Thank you2
Thank you2
Thank you2
Thank you2
Thank you2
Thank you2
]

[
Code:
//Thread Method - Interrupted Method
public void run(){
int i = 0;
while(i<8){
try {
Thread.sleep(8);
} catch (InterruptedException e) { //Interrupted Method
throw new RuntimeException(e);
}
i++;
}
}
}
public void run(){
int j = 0;
while(j<8){
System.out.println("Thank you2");
j++;
}
}
}
public class cwh_75_thread_method {
t1.start();
t2.start();
}
}
Output:
Thank you
Thank you2
Thank you2
Thank you2
Thank you2
Thank you2
Thank you2
Thank you2
Thank you2
Thank you

Thank you
Thank you
Thank you
Thank you
Thank you
Thank you
]

[
Code:
//write a program to print "good morning" and "welcome" continuously till an end point in Java
using Threads
class Practice13a extends Thread{
public void run(){
int i = 0;
while(i<8){
System.out.println("good morning");
i++;
}
}
}
class Practice13b extends Thread{
public void run(){
int i = 0;
while(i<8){
System.out.println("Welcome");
i++;
}
}
}
public class cwh_76_practice13 {
Practice13a p1 = new Practice13a();
Practice13b p2 = new Practice13b();
p1.start();
p2.start();
}
}
Output:
good morning
good morning
good morning
good morning
good morning
good morning
good morning
good morning
Welcome
Welcome
Welcome

Welcome
Welcome
Welcome
Welcome
Welcome
]

[
Code:
using Threads
//Then add sleep method to this, and delay the execution by 200ms of the Welcome thread
public void run(){
int i = 0;
while(i<8){
i++;
}
}
}
public void run(){
int i = 0;
while(i<8){
try {
Thread.sleep(200);
}
catch (InterruptedException e) {
}
i++;
}
}
}
p1.start();
p2.start();
}
}
Output:
good morning
good morning
good morning
good morning
good morning
good morning
good morning
good morning

Welcome
Welcome
Welcome
Welcome
Welcome
Welcome
Welcome
Welcome
]

[
Code:
using Threads
//Then add sleep method to this, and delay the execution by 200ms of the Welcome thread
//Then Demonstrate setPriority() and getPriority() methods in Java
public void run(){
int i = 0;
while(i<8){
i++;
}
}
}
public void run(){
int i = 0;
while(i<8){
try {
Thread.sleep(200);
}
}
i++;
}
}
}
p1.setPriority(6);
p2.setPriority(9);
System.out.println(p1.getPriority());
//p1.start();
//p2.start();
//If setPriority() is not done, they have normal priority equal
//NORM_PRIORITY value is 5
}
}
Output:
6
9
]

[
Code:
//How do you get the state of a thread in java?
public void run(){
int i = 0;
while(i<8){
i++;
}
}
}
public void run(){
int i = 0;
/* while(i<8){
try {
Thread.sleep(200);
}
}
i++;
}*/
}
}
p1.setPriority(6);
p2.setPriority(9);
//p1.start();
System.out.println(p2.getState());
p2.start();
System.out.println(p2.getState());
//getState() gives the state of the thread
}
}
Output:
6
9
NEW
RUNNABLE
]

[
Code:
//How do you get reference to the current thread in Java? - using currentThread()
public void run(){
int i = 0;
while(i<8){
i++;
}
}
}
public void run(){
int i = 0;
while(i<8){
try {
Thread.sleep(200);
}
}
i++;
}
}
}
p1.setPriority(6);
p2.setPriority(9);
//p1.start();
// System.out.println(p2.getState());
p2.start();
//System.out.println(p2.getState());
System.out.println(Thread.currentThread());
}
}
Output:
6
9
Thread[#1,main,5,main]
Welcome
Welcome
Welcome

Welcome
Welcome
Welcome
Welcome
Welcome
]
[
Code:
public class cwh_78_errors {
//Write a program to print all prime numbers between 1 to 10
System.out.println(2);
for(int i=1; i<5; i++){
System.out.println(2*i+1);
//this is logical error as it prints odd numbers and not prime numbers
}
}
}
Output:
2
3
5
7
9
]
[
Code:
//Arithmetic exception example
public class cwh_80_try {
int a = 6000;
int b = 0;
int c = a/b;
System.out.println("the result is "+ c);
}
}

Output:
Exception in thread "main" java.lang.ArithmeticException: / by zero
at com.company.cwh_80_try.main(cwh_80_try.java:7)
]
[
Code:
//Solving Arithmetic Exception of division by zero using Try catch block
public class cwh_80_try {
int a = 6000;
int b = 0;
try{
int c = a/b;
System.out.println("the result is "+ c);
}catch(Exception e){
System.out.println("We couldnt divide because of ");
}
}
}
Output:
We couldnt divide because of
java.lang.ArithmeticException: / by zero
]

[
Code:
//How to hancle specific exceptions.
//Handling specific type of exceptions
marks[0] = 7;
marks[1] = 56;
marks[2] = 6;
System.out.println("Enter the array index: ");
int ind = sc.nextInt();
System.out.println("Enter the number with which you want to divide the value with: ");
int number = sc.nextInt();
try{
System.out.println("The value of the value at index entered is : "+ marks[ind]);
System.out.println("The array of array-value/number is : "+ marks[ind]/number);
System.out.println("Some Exception error occurred!");
}
}
}
Output:
Enter the array index:
1
Enter the number with which you want to divide the value with:
23
The value of the value at index entered is : 56
The array of array-value/number is : 2
]

[
Code:
//How to hancle specific exceptions.
//Handling specific type of exceptions
marks[0] = 7;
marks[1] = 56;
marks[2] = 6;
System.out.println("Enter the array index: ");
System.out.println("Enter the number with which you want to divide the value with: ");
int number = sc.nextInt();
try{
System.out.println("The value of the value at index entered is : "+ marks[ind]);
System.out.println("The array of array-value/number is : "+ marks[ind]/number);
}catch(ArithmeticException e){
}catch(ArrayIndexOutOfBoundsException e){
}
}
}
Output:
Enter the array index:
4
Enter the number with which you want to divide the value with:
2
Some Exception error occurred!
java.lang.ArrayIndexOutOfBoundsException: Index 4 out of bounds for length 3
]

[
Code:
//nested try catch have levels
public class cwh_82_nested_try_catch {
marks[0] = 7;
marks[1] = 56;
marks[2] = 6;
try{
System.out.println("We are in try level 1");
try{
}catch(ArrayIndexOutOfBoundsException e){
System.out.println("Sorry this index does not exist");
System.out.println("Exception in level 2");
}
}catch(Exception e) {
}
}
}
Output:
We are in try level 1
Sorry this index does not exist
Exception in level 2
]

[
Code:
marks[0] = 7;
marks[1] = 56;
marks[2] = 6;
System.out.println("Enter the value of index: ");
try{
try{
System.out.println(marks[ind]);
}
catch(ArrayIndexOutOfBoundsException e){
}
}
catch(Exception e) {
}
}
}
Output:
Enter the value of index:
1
56
]

[
Code:
import org.w3c.dom.ls.LSOutput;
int[] marks = new int[5];
marks[0] = 7;
marks[1] = 56;
marks[2] = 6;
boolean flag = true;
while (flag) {
System.out.println("Enter the value of index: ");
try {
try {
System.out.println(marks[ind]);
flag = false;
} catch (ArrayIndexOutOfBoundsException e) {
}
} catch (Exception e) {
}
}
System.out.println("Thank you for using the program");
}
}
Output:
Enter the value of index:
1
56
Thank you for using the program
]

[
Code:
class MyException extends Exception{
@Override
public String toString(){
return super.toString() + " I am toString()";
}
public String getMessage(){
return super.getMessage() + " I am getMessage()";
}
}
public class cwh_83_exception_class {
public static void main(String[] args) throws MyException {
int a;
System.out.println("enter a: ");
a = sc.nextInt();
if (a<9){
try {
throw new MyException();
System.out.println(e.getMessage());
}
}
}
}
Output:
enter a:
4
null I am getMessage()
]

[
Code:
//Harry made a function. Shivam tries to use it. Harry can warn shivam that there is a
possibilty of exception
//Shivam should accrodingly create a try catch block
public class cwh_84_throw_throws {
public static int divide(int a, int b) throws ArithmeticException{
//Made by Harry
int result = a/b;
return result;
}
//Shivam - uses divide function created by Harry
try{
int c = divide(6, 0);
}
catch(Exception e){
System.out.println("Exception");
}
}
}
Output:
Exception
]

[
Code:
class MyException extends Exception{
@Override
public String toString(){
return" I am toString()";
}
public String getMessage(){
return " I am getMessage()";
}
}
public class cwh_83_exception_class {
public static void main(String[] args) throws MyException {
int a;
System.out.println("enter a: ");
a = sc.nextInt();
if (a<9){
try {
throw new ArithmeticException("This is an Exception") ;
System.out.println(e.getMessage());
System.out.println("Finished");
}
System.out.println("Yes Finished");
}
}
}
Output:
enter a:
3
This is an Exception
Finished
Yes Finished
]

[
Code:
//code in finally block is always executed no matter what even if it is an exception
public class cwh_85_finally {
try{
int a = 5;
int b = 0;
int c = a/b;
}
finally {
System.out.println("This is the end of program");
}
}
}
Output:
This is the end of program
]
[
Code:
public static int greet() {
try {
int a = 50;
int b = 2;
int c = a / b;
return c;
} finally {
System.out.println("This is the end of program");
}
return 0;
}
int k = greet();
}
}

Output:
This is the end of program
25
]
[
Code:
try {
int a = 50;
int b = 10;
int c = a / b;
return c;
} finally {
System.out.println("Cleaning up resources... This is the end of program");
}
return 0;
}
int k = greet();
}
}
Output:
Cleaning up resources... This is the end of program
5
]

[
Code:
try {
int a = 50;
int b = 10;
int c = a / b;
return c;
} finally {
}
return 0;
}
int k = greet();
int a = 7;
int b = 0;
while(true){
try{
System.out.println(a/b);
break;
}
finally {
System.out.println("I am finally value for b = " + b);
}
} b--;
}
}
Output:
5
I am finally value for b = 0
]

[
Code:
try {
int a = 50;
int b = 10;
int c = a / b;
return c;
} finally {
}
return 0;
}
int k = greet();
int a = 7;
int b = 0;
while(true){
try{
System.out.println(a/b);
break;
}
finally {
System.out.println("I am finally value for b = " + b);
}
} b--;
try{
System.out.println(50/10);
}finally{
System.out.println("Yes this is final");
}
}
}
Output:
5
I am finally value for b = 0
5
Yes this is final
]

[
Code:
//Problem - demonstrate syntax error and logical error and runtime error
// Syntax error - int a = 7
int age = 78;
int year_born = 2000 - 78; //Logical error
// Runtime error - System.out.println(6/0);
System.out.println("SOLVED");
}
}
Output:
SOLVED
]
[
Code:
//Problem - write a Java program that prints "HaHa" during Arithmetic exception and "HeHe" durig
//Illegal Argument exception
try{
int a =666/9;
}
catch(IllegalArgumentException e){
System.out.println("HeHe");
}
catch(ArithmeticException e){
System.out.println("HaHa");
}
System.out.println("Finished");
}
}
Output:
Finished
]

[
Code:
//Problem - write a program that allows you to keep accessing the array until a valid index is
given
// if max retries exceed 5 then print error
boolean flag = true;
marks[0] = 7;
marks[1] = 56;
marks[2] = 6;
int index;
int i = 0;
while(flag && i<5){
try{
System.out.println("Enter index ");
index = sc.nextInt();
System.out.println("The value of marks[index] is " + marks[index]);
i++;
break;
System.out.println("Invalid Index");
}
}
}
}
Output:
Enter index
3
Invalid Index
Enter index
2
The value of marks[index] is 6
]

[
Code:
// ArrayList, TreeSet, Set are all part of Collection Framework
import java.util.ArrayList;
import java.util.Set;
import java.util.TreeSet;
public class cwh_89_collections {
// ArrayList
// Set
// TreeSet
System.out.println("Done");
}
}
Output:
Done
]
[
Code:
//ArrayList - Advanced Java
// ArrayList can be resized, can we start inserting from a particular index,
// we can do things we wont be able to do with normal array
import java.lang.reflect.Array;
import java.util.*;
public class cwh_91_arraylist {
ArrayList<Integer> l1 = new ArrayList<>();
l1.add(6);
l1.add(7);
l1.add(4);
l1.add(6);
l1.add(5);
for(int i=0; i<l1.size(); i++){
System.out.println(l1.get(i)); //get() method is used to get ith element from
arraylist
}
}
}

Output:
6
7
4
6
5
]
[
Code:
import java.util.*;
ArrayList<Integer> l2 = new ArrayList<>(5);
l2.add(15);
l2.add(18);
l2.add(19);
l1.add(6);
l1.add(7);
l1.add(4);
l1.add(6);
l1.add(5);
l1.add(0,5);
l1.addAll(l2);
System.out.println(l1.get(i)); //get() method is used to get ith element from
arraylist
}
}
}

Output:
5
6
7
4
6
5
15
18
19
]

[
Code:
//All important Methods of ArrayList
import java.util.*;
l2.add(15);
l2.add(18);
l2.add(19);
l1.add(6);
l1.add(7);
l1.add(4);
l1.add(6);
l1.add(5);
l1.add(0,5);
l1.addAll(l2);
System.out.println(l1.contains(7));
System.out.println(l1.indexOf(7));
System.out.print(l1.get(i)); //get() method is used to get ith element from
arraylist
System.out.print(", ");
}
}
}
Output:
true
2
5, 6, 7, 4, 6, 5, 15, 18, 19,
]

[
Code:
//All important Methods of ArrayList
import java.util.*;
l2.add(15);
l2.add(18);
l2.add(19);
l1.add(6);
l1.add(7);
l1.add(4);
l1.add(6);
l1.add(5);
l1.add(0,5);
l1.addAll(l2);
System.out.println(l1.contains(7));
System.out.println(l1.indexOf(7));
System.out.println(l1.lastIndexOf(6));
//l1.clear(); --> for emptying
System.out.print(l1.get(i)); //get() method is used to get ith element from
arraylist
System.out.print(", ");
}
}
}
Output:
true
2
4
5, 6, 7, 4, 6, 5, 15, 18, 19,
]

[
Code:
import java.util.ArrayDeque;
public class cwh_93_arraydeque {
ArrayDeque<Integer> ad1 = new ArrayDeque<>();
ad1.add(6);
ad1.add(56);
System.out.println(ad1.getFirst());
System.out.println(ad1.getLast());
}
}
Output:
6
56
]
[
Code:
//Hashset in Java
import java.util.HashSet;
//Default initial capacity is 16 and load factor is 0.75
public class cwh_95_set {
HashSet<Integer> myHashSet = new HashSet<>(6, 0.5F);
myHashSet.add(1);
myHashSet.add(11);
myHashSet.add(23);
myHashSet.add(12);
myHashSet.add(8);
System.out.println("HashSet is :");
System.out.println(myHashSet);
}
}
Output:
HashSet is :
[1, 23, 8, 11, 12]
]

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