Methods In Java

Methods

There are two stages in methods

1.       Declaring the methods.

2.       Calling the methods.

Declaring the methods.

·         In this stage we give a name to the method and it’s return[D1]  type. We can give any name to a method. But in the run time pc only execute the codes in the main method.

Example: class cal{ void add(){ int x=2; int y=3; System.out.println  (“sum = ” + (x+y )); } void sub(){ int x=2; int y=3; System.out.println  (“sub = ” + (x-y )); } void mul(){ int x=2; int y=3; System.out.println  (“mul = ” + (x*y )); } void div(){ int x=2; int y=3; System.out.println  (“div = ” + (x/y )); } }

                                                                                                                                                                               
In the above example there is no main method. Therefore the output should be empty.

output

so we should call them in to the main method.

Real world entity has set of properties and set of behaviours.

Ex :-

Entity: person

Properties: name, age, date of birth, weight

Behaviours: run, jump, talk         

1.       Real world entity can be represented by a java class.

2.       The properties of the entity will be map to variable.

3.       The behaviours of the entity will be map to methods.

class person {   int age= 23; String name = “Kamal”; Int height = 125; int weight = 90;     void run(){                   //////////////                                 ///////////////// }                 void run(){                                 //////////////                                 ///////////////// } }

Object orient programming concept.

Object/entity : -

·         Object In the real world can be represented from a java class.

Properties /atribures : -

·         Properties In the entity are map to global variable in the java class.

The behaviours : -

·         The behaviours in the entity are map to methods in the java class.

Formore about Object orient programming concept.

1  Public static void main (String args[]){ 2                                Calculator c1= new Calculator(); 3                                       c1.add(); 4                                       c1.subs(); 5                                       c1.mul(); 6                                       c1.div(); 7                                       c1.mod(); 8 }

To call a method / variable in a class an object/instant must be created of the given class.

        Calculator c1= new Calculator (); 

Calculator                            : reference data type ( Hold the reference memory address of the calculator object)

c1                                            : variable name

 new Calculator ();           : create the calculator object

·         multiple classes can be declared with different with different names.

·         An object/instant can be created out of each declared class.

·         Therefore each declared class type can become a reference   data type.

Method parameters

The compiler identifies / differentiate a method using the method signature.

class Calculator{ void add ( int x , int y ){                  System.out.println(); } public static void main(String args[]){ Calculator c1= new Calculator();              c.add( 2,3); c.add(-2,10); } }

In the line   void add ( int x , int y ){ , the method parameters are int x , int y  .

             c.add( 2,3);

c.add(-2,10);

2,3 ; -2,10 are method arguments .

  

Method overloading.

Declaring multiple methods in a class with the same method name but with different method parameters.

class Calculator{ void add ( int x , int y ){                        System.out.println(); } void add ( double x , double y ){                        System.out.println(); }        public static void main(String args[]){        Calculator c1= new Calculator();                     c.add( 2,3);        } }

Method return types.

class Test{                 void m(){ -----------------------------------à no value will be return. int x; x=10; int y =3; System.out.println(“Total = ”+ (x+y) ); }                 int d(){  -----------------------------à int value will be return. int x; x=10; int y =3; System.out.println(“Total = ”+ (x+y) ); Return ( x+y );              ->>>>>>>> return statement }              public static void main (String args []){ Test t= new Test();            t.m();            int x = t.d();            System.out.println ( x ); } }

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VARIABLES

There are two stages in a Variable.

1.       Declaring the variable.

2.       Initializing the variable.

Declaring the variable.

·         Introduce compiler about the variable type.

Initializing the variable.

·         Give a value to variable.

class Test{           public static void main (String args []){ int x;                // Declaring the variable. x=10;               // Initializing the variable. System.out.println(x); } }

Ex 1:

java programme to print the value of x and y.

class Test{             public static void main (String args []){ int x; x=10; int y =3; System.out.println(“x = ”+ x+“, y = ”+y); } }

Ex 1:

java programme to print the sum of x and y.`

class Test{             public static void main (String args []){ int x; x=10; int y =3; System.out.println(“x = ”+ x+“, y = ”+y); System.out.println(“Total = ”+ (x+y) ); } }

Data types.

       

    

Primitive Data types.

byte	8 bits	Default data type for whole numbers.
short	16 bits
int	32 bits
long	64 bits
float	32 bits	Default data type for decimals.
double	64 bits
char	16 bits
boolean	1 bits