Java - Overloading - Methods

In this tutorial we will learn about method overloading in Java programming language.

What is overloading of methods in Java?

In Java when more than one method share the same name but different parameter declaration then the methods are said to be overloaded and the process is called method overloading.

Syntax

class NameOfTheClass {
  
  access_modifier return_type methodName(list_of_params_1) {
    // some code...
  }

  access_modifier return_type methodName(list_of_params_2) {
    // some code...
  }
}

Where, NameOfTheClass is the name of the class and it have two methods sharing the same name methodName but they have different parameter declaration.

Example #1:

In the following example we the Compute class having area method that is overloaded.

If we pass single argument to the method then we are computing the area of a square. And if we pass two arguments then we are computing the area of a rectangle.

class Compute {

  // this method will compute the area of a square
  public double area(double side) {
    return side * side;
  }

  // this method will compute the area of a rectangle
  public double area(double length, double breadth) {
    return length * breadth;
  }
}

class MethodOverloadingExample {
  public static void main(String[] args) {
    // create object
    Compute obj = new Compute();

    // variable
    double area, side, length, breadth;

    // find the area of a square
    side = 12.5;
    area = obj.area(side);
    System.out.println("Area of square having side " + side + " is " + area);

    // find the area of a rectangle
    length = 10.6;
    breadth = 20;
    area = obj.area(length, breadth);
    System.out.println("Area of rectangle having length " + length + " and breadth " + breadth + " is " + area);
  }
}

Output:

$ javac MethodOverloadingExample.java 
$ java MethodOverloadingExample
Area of square having side 12.5 is 156.25
Area of rectangle having length 10.6 and breadth 20.0 is 212.0

Example #2:

In the following example we are creating a Happy class having isHappy method that is overloaded.

The first method is:

public void isHappy(boolean happy) {
}

It takes boolean value as argument and prints an output message based on the argument value.

The second method is:

public boolean isHappy(int happinessLevel) {
}

This takes an integer argument and based on the value it returns a boolean value back to the calling method. We can then use the returned value and some suitable output message.

Code

class Happy {

  // this method will print the output based on boolean value passed
  public void isHappy(boolean happy) {
    if (happy == true) {
      System.out.println("Person is happy :)");
    } else {
      System.out.println("Person is sad :(");
    }
  }

  // this method will return boolean value
  public boolean isHappy(int happinessLevel) {
    if (happinessLevel > 5) {
      return true;
    } else {
      return false;
    }
  }
}

class MethodOverloadingExample {
  public static void main(String[] args) {
    // create object
    Happy person = new Happy();

    // passing boolean value and printing result
    System.out.println("Is person happy? ");
    person.isHappy(true);

    // passing integer value and getting back boolean value
    int happinessLevel = 5;
    boolean isPersonHappy = person.isHappy(happinessLevel);

    // now using the isPersonHappy boolean value and calling the method
    System.out.println("Happiness Level " + happinessLevel);
    person.isHappy(isPersonHappy);
  }
}

Output:

$ javac MethodOverloadingExample.java 
$ java MethodOverloadingExample
Is person happy? 
Person is happy :)
Happiness Level 5
Person is sad :(