OOPS in JAVA 5

OOPS in JAVA 5

Method Overloading in Java

If a class have multiple methods by same name but different parameters, it is known as Method Overloading. 

Advantage of method overloading:

Method overloading increases the readability of the program.

Different ways to overload the method:

1. By changing number of arguments.

2. By changing the data type.

NOTE : In java, Methood Overloading is not possible by changing the return type of the method.

In this reference of an argument is pass to a method. Any changes made inside the method will affect the agrument value.

Different ways of Method overloading

1. Method overloading by changing data type of Arguments:

Example 

class Calculate
{
 void sum (int a, int b)
 {
  System.out.println("sum is"+(a+b)) ;
 }
 void sum (float a, float b)
 {
  System.out.println("sum is"+(a+b));
 }
 Public static void main (String[] args)
 {
  Calculate  cal = new Calculate();
  cal.sum (8,5);      //sum(int a, int b) is method is called. 
  cal.sum (4.6, 3.8); //sum(float a, float b) is called.
 }
}
Output :
Sum is 13
Sum is 8.4

You can see that sum() method is overloaded two times. The first takes two integer arguments, the second takes two float arguments.

2. Method overloading by changing no. of argument:

Example 

class Area
{
 void find(int l, int b)
 {
  System.out.println("Area is"+(l*b)) ;
 }
 void find(int l, int b,int h)
 {
  System.out.println("Area is"+(l*b*h));
 }
 public static void main (String[] args)
 {
  Area  ar = new Area();
  ar.find(8,5);     //find(int l, int b) is method is called. 
  ar.find(4,6,2);    //find(int l, int b,int h) is called.
 }
}
Output :
Area is 40
Area is 48

In this example the find() method is overloaded twice. The first takes two arguments to calculate area, and the second takes three arguments to calculate area.

Example of Method overloading with type promotion.

class Area
{
 void find(long l,long b)
 {
  System.out.println("Area is"+(l*b)) ;
 }
 void find(int l, int b,int h)
 {
  System.out.println("Area is"+(l*b*h));
 }
 public static void main (String[] args)
 {
  Area  ar = new Area();
  ar.find(8,5);     //automatic type conversion from find(int,int) to find(long,long). 
  ar.find(2,4,6)    //find(int l, int b,int h) is called.
 }
}
Output :
Area is 40
Area is 48

Q. Why Method Overloaing is not possible by changing the return type of method???

In java, method overloading is not possible by changing the return type of the method because there may occur ambiguity. Let's see how ambiguity may occur. because there was problem.

class Calculation3{  
  int sum(int a,int b){System.out.println(a+b);}  
  double sum(int a,int b){System.out.println(a+b);}  
  
  public static void main(String args[]){  
  Calculation3 obj=new Calculation3();  
  int result=obj.sum(20,20); //Compile Time Error  
  
  }  
}

int result=obj.sum(20,20); //Here how can java determine which sum() method should be called.

Variable Arguments(var-args):

typeName... parameterName

In the method declaration, you specify the type followed by an ellipsis (...) Only one variable-length parameter may be specified in a method, and this parameter must be the last parameter. Any regular parameters must precede it.

Example

public class VarargsDemo {

   public static void main(String args[]) {
      // Call method with variable args  
	  printMax(34, 3, 3, 2, 56.5);
      printMax(new double[]{1, 2, 3});
   }

   public static void printMax(double... numbers) {
   if (numbers.length == 0) {
      System.out.println("No argument passed");
      return;
   }

   double result = numbers[0];

   for (int i = 1; i <  numbers.length; i++)
      if (numbers[i] >  result)
      result = numbers[i];
      System.out.println("The max value is " + result);
   }
}
Output:

The max value is 56.5
The max value is 3.0