Data Handling and Function

Java/J2EE Programming Training
Data Handling and Functions

Classification: Restricted
Agenda
• Implement Single and Multi dimensional array
• Declare and Define Functions
• Call Functions by value and by reference
• Implement Method Overloading
• Use String data-type and String-buffer

Introduction to Arrays

Meet John Again

One day in office

One day in office
6

John’s Project – Question Statement

Daisy was Confused!

John already had a plan

John Came up with a solution

John’s Solution

John Presented the Solution

John gets a Promotion

Why do we use Arrays?
• Arrays are an important structure to hold data.
• Java allows us to hold many objects of the same type using arrays and it can
be used with the help of a loop to access the elements by their index.

Arrays

Declaring Arrays

Declaring Arrays
• Arrays can be declared for primitive and non-primitive data types.
• Instead of declaring int a1, a2, a3, a4....a100, we can declare int
a[100].
• It is fast and efficient to access an element in an array using the
corresponding index without actually traversing through the entire
array.
• The size of the array is fixed once it is created.
• For Example: A character array of 10 characters can be declared as

Types of Arrays

How Single Dimensional Arrays are used?

Multidimentional Array
• Multi dimensional arrays can be 2 dimensional as rows and columns similar
to a matrix or it could be 3 dimensional with depth, height and breadth or it
could be 'n' dimensional array as per the requirement.
• Multi-dimensional arrays can be declared as
• Usually 2 dimensional arrays are used to perform matrix operations.
• Like single dimensional arrays, multi dimensional arrays can be of primitive
and nonprimitive data type.

Question
How many bytes are allocated for the array x?
int x[][] = new int[5][5];

Answer
An int element takes 4 bytes and array x can store 25
int elements.
Hence total number of bytes taken by x is 25*4 = 100

Question
Can we do multi dimensional array operations in
single dimensional array?
If yes, then why do we require multi dimensional
array?

Answer
We can perform all the operations of multi
dimensional array in single dimensional array but
when the data has more than one dimension, it will
be easier to perform operations in multi
dimensional array.

LAB

Function

Daisy Seek’s Help

John helps Daisy

John explain Functions

Functions
• Scope specifier modifier return type function name (arguments)
• A function/method has group of statements to be executed.
• A function has a task to perform.
• A function is declared as public static void say Hello(int a, int b)

Why do we use functions?
• We use functions to provide different kinds of functionality.
• For example:
• absolute()
• To find the absolute value of a number.
• square()
• To find the square of a number.
• sqrt()
• To find the square root of a number.

Features of Functions
• Scope specifier
• This option specifies the visibility of the function. It could be public,
private, protected or default (package).
• Modifier
• This is optional.
• This will change the meaning of the function. Some of the options could
be final, static, native,synchronized etc.
• Return type
• This option specifies the data that will be returned by the function.
• It could be primitive data type or objects.
• Function name
• It is the name given to the function. Using function name, functions can
be invoked.
• Arguments
• This is optional but can be used. Using this, one can pass values to the
function for computation.

What happens when a Function is Invoked?
• When a function is called from the main method, main method() address is
stored on top of the stack.
• Control jumps to execute the function.
• After executing the function, main method address is popped from the
stack and main
method execution resumes.

What happens when a function is invoked?

What happens when a Function is Invoked?

Sample program on Function

Sample program on Functions (Contind..)

Sample program on Functions(Contd..)
4

Sample Program on Functions (contd..)

Function Calling ways

Call by Value
• When value of the
primitive data type is
passed as an argument
from the calling
function, data is being
sent to the function.
• At the receiving end, a
new variable is created
and the data is copied.
This is call by value.
• All the programs we
have done till now
is done using call by
value.

Call by Reference

Polymorphism

Function Overloading

Function Overloading (contd.)

Function Overloading
5

Program on Function Overloading

Meet Mr. Letter and Miss Sentence!

Mr.Letter is from “char datatype”

Miss Sentence is sad!

Miss Sentence has her own Place in Java

Why do we use String?

String
• String is a class in Java to store string data.
• You can assign string data simply by defining the string object and assign
the string like this:
• You can concatenate two string using + symbol.
• For Example:
• Output of the program is
• Appended string is: HelloWorld
String str;
String str = “Focusthread”
String str = new String (“Focusthread”);

Where do we use string?

String Functions
• length()
• Returns the length of the string.
• charAt(int)
• Returns a character at the specified position. Index of the String starts from 0.
• concat (String str)
• It concatenates the with the string object. It is same as using '+' operator for
concatenation.
• equals(String str)
• Checks whether string object and str and return true if they are same else
returns false.
• EqulsIgnoreCase (String str)
• Same as above function except that this function ignores the case and checks
for the equality of the strings.
• indexOf(String str)
• Returns the index of the specified string in the string object.
• lastIndexOf(String str)
• Same as above function but checks from back of the string.

String Functions
• replace(char ch, char ch1)
• Replaces the character ch with Character ch1 in the string.
• toLowerCase()
• Converts the given string to lowercase.
• toUpperCase()
• Converts the given string to uppercase.
• trim()
• Removes the leading and trailing spaces of the string.

StringBuffer

Question
When should we use String and
StringBuffer? why?

Answer
When we do not need to modify string objects then
String can be used else using StringBuffer is a better
option since it is mutable.

Program on StringBuffer

StringBuider

StringBuilder Constructors

Assignment – Single Dimentional Array

Assignment – Two Dimentational Array

Assignment - Functions

Assignment – Functions Overloading

Module Assignment

Agenda for Next Class

Pre work

Thank You

Data Handling and Function

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