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Methods

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Method

A method is a group of programming

language statements with a given name.

Method syntaxReturntype methodname (parameters)

{

statement 1;

statement 2;

..

}

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void sum ( int a, int b )

{

statement 1

statement 2..

}

Declaration

Body

Method has two major parts:

1. Method Declaration

2. Method Body

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Method that does not return a value

If a method does not return a value, itsreturn type must be declared void.

For example:

voidabc( )

{System.out.println(Hello World);

}

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Method that returns a value

Methods that have a return type otherthan void return a value to the calling

routine using the following form of the

return statement.

return value;

int abc( ){

return 5+5;

}

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Class

Methods(static methods)

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The class (static) methods is not

referenced through a particular instance

of a class but through the class itself.

You dont have to create an object of

the class to invoke a static method.

Creating Static Methods

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static Returntype methodname (parameters)

{statement 1;

statement 2;

..

}

Static Method Syntax

staticvoiddisplay(int a, int b)

{

System.out.println(a+b);

}

example

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Class Methodsvs.

Instance Methods

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All objects have their own

copy of instance method.

All objects share the single

copy of static method.

instance methods are

declared without statickeyword.

Static methods are declared

by using static keyword.

Instance MethodStatic Method

Static vs. Instance Methods

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Instance method cannot be

invoked without creating an

object.

ObjectName.method( );

Static method can be

invoked without creating an

object, by using class name.

ClassName.method( );

Instance method depends on

the object for which it is

available.

Static method does not

depend on the single object

because it belongs to a class.

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Instance methods can refer

tothisand super.

Static methods cannot refer

to this orsuper.

Non-static methods canaccess static variables.

Static methods cannotaccess not-static variables.

Non-static methods can call

static methods.

Static methods cannot call

non-static methods.

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There are also static blocks of code in java,

which have the following syntax:

static

{statements;

}

These blocks are used to initialize thevariables and execute at class load time.

Static Blocks

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static

import

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static import

J2SE 5.0 introduces a new feature calledstatic import that lets you import the static

variable of a class so that you can refer to

them without having to mention the classname.

import static java.lang.Math.PI;

import static java.lang.System.out;

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Methodswith variable length

parameters

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Method with variable length parameters

J2SE 5.0 introduces a new feature that letsyou define methods with a variable number

of parameters, so that you can make several

method calls with a variable number of

arguments.

These methods are called variable-lengthargument methods.

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Syntax

The variable-length parameters list consistsof a type followed by three dots and the

variable name.

public voidprint(int... values)

{

for(int i: values)

{

System.out.println(i);}

}

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Note

There must be only one variable lengthparameter list in the method.

Following method is invalid

public voidprint(int... a, int... b)

{

}

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Note

If there are individual parameters in additionto the list, the variable length parameters list

must appear last inside the parameters of the

method.

Following method is valid:

public voidprint(String s, int... b){

}

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Method

Overloading

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Method Overloading

In java, it is possible to define two or moremethods with the same name, within the

same class.

They share the same name as long as their

parameters are different.

This process is known as methodoverloading.

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When java call an overloaded method, it

simply executes the version of the

method whose parameters match the

arguments.

Two methods are overloaded if there:

1. No of parameters are different2. Type of parameters is different

3. Order of parameters is different

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1.No of parameters are different

publicvoidadd(int i)

{

System.out.println(i+i);

}

publicvoidadd(int i, int j)

{

System.out.println(i+j);

}

publicvoidadd(int i, int j, int k){

System.out.println(i+j+k);

}

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2.Type of parameters is different

publicvoidadd(int i, int j)

{

System.out.println(i+j);

}

publicvoidadd(double i, double j)

{

System.out.println(i+j);

}

publicvoidadd(double i, int j){

System.out.println(i+j);

}

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3.Order of parameters is different

publicvoidadd(double i, int j)

{

System.out.println(i+j);

}

publicvoidadd(int i, double j)

{

System.out.println(i+j);

}