Home » Java Book » Class » Class Creation » Method »

Syntax for Method Creation

This is the general form of a method:


type methodName(parameter-list) { 
    // body of method 
}

type specifies the returned type.

If the method does not return a value, its return type must be void.

The parameter-list is a sequence of type and identifier pairs separated by commas.

Parameters receive the arguments passed to the method.

If the method has no parameters, the parameter list will be empty.

Return statement

return statement has the following form:


return value;

value is the returned value.

Adding a Method to the Class

Add a method to Box,as shown here:

 
class Box {
  int width;
  int height;
  int depth;
  void calculateVolume() {
    System.out.print("Volume is ");
    System.out.println(width * height * depth);
  }
}

public class Main {

  public static void main(String args[]) {
    Box mybox1 = new Box();
    mybox1.width = 10;
    mybox1.height = 20;
    mybox1.depth = 15;

    mybox1.calculateVolume();

  }
}

This program generates the following output:


Volume is 3000

Returning a Value

We can use return statement to return a value to the callers.

 
class Rectangle {
  int width;
  int height;

  int getArea() {
    return width * height;
  }
}

public class Main {

  public static void main(String args[]) {
    Rectangle mybox1 = new Rectangle();
    int area;
    mybox1.width = 10;
    mybox1.height = 20;

    area = mybox1.getArea();
    System.out.println("Area is " + area);

  }
}

The output:


Area is 200

In this line the return statement returns value from the getArea()method. And the returned value is assigned to area.


    area = mybox1.getArea();

The actual returned data type must be compatible with the declared return type . The variable receiving the returned value (area) must be compatible with the return type.

The following code uses the returned value directly in a println( ) statement:


    System.out.println("Area is " + mybox1.getArea());

Returning Objects

A method can return class types.

 
class MyClass {
  int myMemberValue = 2;
  MyClass() {
  }
  MyClass doubleValue() {
    MyClass temp = new MyClass();
    temp.myMemberValue = temp.myMemberValue*2;
    return temp;
  }
}

public class Main {
  public static void main(String args[]) {
    MyClass ob1 = new MyClass();
    ob1.myMemberValue =2;
    MyClass ob2;

    ob2 = ob1.doubleValue();
    System.out.println("ob1.a: " + ob1.myMemberValue);
    System.out.println("ob2.a: " + ob2.myMemberValue);

    ob2 = ob2.doubleValue();
    System.out.println("ob2.a after second increase: " + ob2.myMemberValue);
  }
}

The output generated by this program is shown here:


ob1.a: 2
ob2.a: 4
ob2.a after second increase: 4

« Method

Recursion »

java2s.com | Contact Us | Privacy Policy

All other trademarks are property of their respective owners.