JAVA LOOP.pptx

JAVA LOOP
• In computer programming, loops are used to repeat a block of
code. For example, if you want to show a message 100 times,
then rather than typing the same code .

Types of LOOPS
• in Java, there are three types of loops: for, while, and do-
while. The for loop is used for a known number of iterations, the
while loop is used for an unknown number of iterations based
on a condition, and the do-while loop is similar to the while loop,
but the code block is executed at least onceV

For loop
• Java for loop is used to run a block of code for a certain number of
times. The syntax of for loop is:
for (initialExpression; testExpression; updateExpression) {
// body of the loop
}

For loop
The initial expression initializes
and/or declares variables and
executes only once.
The condition is evaluated. If the
condition is true, the body of the
for loop is executed.
The update Expression updates the
value of initialExpression.
The condition is evaluated again.
The process continues until the
condition is false.

Example 1:
int n = 5;
// for loop
for (int i = 1; i <= n; ++i) {
System.out.println("Java is fun");
Output:
Java is fun
Java is fun
Java is fun
Java is fun
Java is fun

Example2:
Java for loop
for(int i=1;i<=10;i++){
System.out.println(i);
}
Output:
1
2
3…. 10

Java while loop
• The Java while loop is used to iterate a part of
the program repeatedly until the specified Boolean condition is
true. As soon as the Boolean condition becomes false, the loop
automatically stops.
• The while loop is considered as a repeating if statement. If the
number of iteration is not fixed, it is recommended to use the
while loop.

While syntax
while (condition){
//code to be executed
Increment / decrement statement
}

example1
1. int i=1;
2. while(i<=10){
3. System.out.println(i);
4. i++;
5. }
Output:
1
2
3... 10

Java while loop
Java while loop is used to run a specific code until a certain condition is
met. The syntax of the while loop is:

A while loop evaluates the textExpression inside the parenthesis ().
If the textExpression evaluates to true, the code inside the while loop is
executed.
The textExpression is evaluated again.
This process continues until the textExpression is false.
When the textExpression evaluates to false, the loop stops.
To learn more about the conditions, visit Java relational and logical
operators.

Example 1:
// declare variables
int i = 1, n = 5;
// while loop from 1 to 5
while(i <= n) {
System.out.println(i);
i++;
Output:
1
2
3…5

Syntax
while (condition){
//code to be executed
Increment / decrement statement
}

Example 1:
1. int i=1;
2. while(i<=10){
4. i++;
5. }

Java do-while Loop
• The Java do-while loop is used to iterate a part of the program
repeatedly, until the specified condition is true. If the number of
iteration is not fixed and you must have to execute the loop at
least once, it is recommended to use a do-while loop.
• Java do-while loop is called an exit control loop. Therefore,
unlike while loop and for loop, the do-while check the condition
at the end of loop body. The Java do-while loop is executed at
least once because condition is checked after loop body.

Syntax
1.do{
2.//code to be executed / loop body
3.//update statement
4.}while (condition);

1.int i=1;
2. do{
4. i++;
5. }while(i<=10);
Output:
1
2
3…10

Java Arrays
• Arrays are used to store multiple values in a single
variable, instead of declaring separate variables for
each value.
• To declare an array, define the variable type
with square brackets:

Array
String[] cars = {"Volvo", "BMW", "Ford", "Mazda"};
To create an array of integers, you could write:
int[] myNum = {10, 20, 30, 40};

Example 1
public static void main(String[] args) {
System.out.println(cars[0]);
}

cars[0] = "Opel";
System.out.println(cars[0]);

for (int i = 0; i < cars.length; i++) {
System.out.println(cars[i]);
Output:
Volvo", "BMW", "Ford", "Mazd

JAVA METHOD
• A method is a block of code which only runs when it is called.
• You can pass data, known as parameters, into a method.
• Methods are used to perform certain actions, and they are also known as
functions.
• Why use methods? To reuse code: define the code once, and use it many
times.
Create a Method
• A method must be declared within a class. It is defined with the name of
the method, followed by parentheses (). Java provides some pre-defined
methods, such as System.out.println(), but you can also create your own
methods to perform certain actions:

int[][] myNumbers = { {1, 2, 3, 4}, {5, 6, 7} };
System.out.println(myNumbers[1][2]); // Outputs 7

Scanner input = new Scanner (System.in);
double totalprice=0;
for (int i=0; i <cars.length ; i++)
{
System.out.println(cars[i]);
System.out.println("Enter price:");
double price = input.nextDouble();
totalprice=(totalprice + price);
}
System.out.println("TOTAL PRICE:" + totalprice);

int[] age = {12, 4, 5, 2, 5};
// access each array elements
System.out.println("Accessing Elements of Array:");
System.out.println("First Element: " + age[0]);
System.out.println("Second Element: " + age[1]);
System.out.println("Third Element: " + age[2]);
System.out.println("Fourth Element: " + age[3]);
System.out.println("Fifth Element: " + age[4]);
}

Example Explained
myMethod() is the name of the method
static means that the method belongs to the
Main class and not an object of the Main class.
You will learn more about objects and how to
access methods through objects later in this
tutorial.
void means that this method does not have a
return value. You will learn more about return
values later in this chapter

Call a Method
To call a method in Java, write the method's name followed by two
parentheses () and a semicolon;
In the following example, myMethod() is used to print a text (the
action), when it is called:

public class Main {
static void myMethod()
{
System.out.println("I just got executed!");
}
public static void main(String[] args)
{
myMethod();
}
}
Inside main, call the myMethod() method:

Creating your own Classes
At the end of the lesson, the student should be able to:
• ● Create their own classes
• ● Declare attributes and methods for their classes
• ● Use the this reference to access instance data
• ● Create and call overloaded methods
• ● Import and create packages
• ● Use access modifiers to control access to class members
•

Java Classes/Objects
• Java is an object-oriented programming language.
• Everything in Java is associated with classes and
objects, along with its attributes and methods. For
example: in real life, a car is an object. The car
has attributes, such as weight and color,
and methods, such as drive and brake.
• A Class is like an object constructor, or a "blueprint" for
creating objects.

A NetBeans project contains the classes needed to build a Java
application. The application uses the main class as the starting point
for the execution of the Java code. In fact, in a new Java application
project created by NetBeans only one class included - the main class
contained within the Main. java file.DELA PEÑA, CARL CUEVAS?
What is the main class in
NetBeans?

get method
The get method returns the value of the variable name . The
set method takes a parameter ( newName ) and assigns it to
the name variable. The this keyword is used to refer to the
current object.

get method
• The get method returns the value of the variable name . The set
method takes a parameter ( newName ) and assigns it to the
name variable. The this keyword is used to refer to the current
object.

• Defining your own classes
• Coding Guidelines
• Declaring Attributes
• Instance Variables
• Class (static) variables
• Declaring Methods
• Accessor Methods
• Mutator Methods
• Multiple return statements
• Static Methods
• “this” reference
• Overloading Methods
• Constructors
• Default Constructor
• Overloading Constructors
• Using Constructors
• “this()” constructor call
• Packages
• Importing Packages
• Creating Packages
• Setting the CLASSPATH
• Access Modifiers
• default accessibility
• public accessibility
• protected accessibility
• private accessibility

JAVA LOOP.pptx

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JAVA LOOP.pptx