• Difficulty Level : Easy
• Last Updated : 17 Feb, 2021

Overloading allows different methods to have the same name, but different signatures where the signature can differ by the number of input parameters or type of input parameters or both. Overloading is related to compile-time (or static) polymorphism.

 `// Java program to demonstrate working of method ` `// overloading in Java. ` ` `  `public` `class` `Sum { ` ` `  `    ``// Overloaded sum(). This sum takes two int parameters ` `    ``public` `int` `sum(``int` `x, ``int` `y) ` `    ``{ ` `        ``return` `(x + y); ` `    ``} ` ` `  `    ``// Overloaded sum(). This sum takes three int parameters ` `    ``public` `int` `sum(``int` `x, ``int` `y, ``int` `z) ` `    ``{ ` `        ``return` `(x + y + z); ` `    ``} ` ` `  `    ``// Overloaded sum(). This sum takes two double parameters ` `    ``public` `double` `sum(``double` `x, ``double` `y) ` `    ``{ ` `        ``return` `(x + y); ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `        ``Sum s = ``new` `Sum(); ` `        ``System.out.println(s.sum(``10``, ``20``)); ` `        ``System.out.println(s.sum(``10``, ``20``, ``30``)); ` `        ``System.out.println(s.sum(``10.5``, ``20.5``)); ` `    ``} ` `} `

Output :

```30
60
31.0
```

Question Arises:
Q. What if the exact prototype does not match with arguments.

Ans.
Priority wise, compiler take these steps:

1. Type Conversion but to higher type(in terms of range) in same family.
2. Type conversion to next higher family(suppose if there is no long data type available for an int data type, then it will search for the float data type).

Let’s take an example to clear the concept:-

 `class` `Demo { ` `    ``public` `void` `show(``int` `x) ` `    ``{ ` `        ``System.out.println(``"In int"` `+ x); ` `    ``} ` `    ``public` `void` `show(String s) ` `    ``{ ` `        ``System.out.println(``"In String"` `+ s); ` `    ``} ` `    ``public` `void` `show(``byte` `b) ` `    ``{ ` `        ``System.out.println(``"In byte"` `+ b); ` `    ``} ` `} ` `class` `UseDemo { ` `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` `        ``byte` `a = ``25``; ` `        ``Demo obj = ``new` `Demo(); ` `        ``obj.show(a); ``// it will go to ` `        ``// byte argument ` `        ``obj.show(``"hello"``); ``// String ` `        ``obj.show(``250``); ``// Int ` `        ``obj.show(``'A'``); ``// Since char is ` `        ``// not available, so the datatype ` `        ``// higher than char in terms of ` `        ``// range is int. ` `        ``obj.show(``"A"``); ``// String ` `        ``obj.show(``7.5``); ``// since float datatype ` `// is not available and so it's higher ` `// datatype, so at this step their ` `// will be an error. ` `} ` `} `

We don’t have to create and remember different names for functions doing the same thing. For example, in our code, if overloading was not supported by Java, we would have to create method names like sum1, sum2, … or sum2Int, sum3Int, … etc.

Can we overload methods on return type?
We cannot overload by return type. This behavior is same in C++. Refer this for details

 `public` `class` `Main { ` `    ``public` `int` `foo() { ``return` `10``; } ` ` `  `    ``// compiler error: foo() is already defined ` `    ``public` `char` `foo() { ``return` `'a'``; } ` ` `  `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `    ``} ` `} `

However, Overloading methods on return type are possible in cases where the data type of the function being called is explicitly specified. Look at the examples below :

 `// Java program to demonstrate the working of method ` `// overloading in static methods ` `public` `class` `Main { ` ` `  `    ``public` `static` `int` `foo(``int` `a) { ``return` `10``; } ` `    ``public` `static` `char` `foo(``int` `a, ``int` `b) { ``return` `'a'``; } ` ` `  `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `        ``System.out.println(foo(``1``)); ` `        ``System.out.println(foo(``1``, ``2``)); ` `    ``} ` `} `

Output:

```10
a
```

 `// Java program to demonstrate working of method ` `// overloading in  methods ` `class` `A { ` `    ``public` `int` `foo(``int` `a) { ``return` `10``; } ` ` `  `    ``public` `char` `foo(``int` `a, ``int` `b) { ``return` `'a'``; } ` `} ` ` `  `public` `class` `Main { ` ` `  `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `        ``A a = ``new` `A(); ` `        ``System.out.println(a.foo(``1``)); ` `        ``System.out.println(a.foo(``1``, ``2``)); ` `    ``} ` `} `

Output:

```10
a
```

The answer is ‘Yes’. We can have two ore more static methods with same name, but differences in input parameters. For example, consider the following Java program. Refer this for details.

Can we overload methods that differ only by static keyword?
We cannot overload two methods in Java if they differ only by static keyword (number of parameters and types of parameters is same). See following Java program for example. Refer this for details.

Can we overload main() in Java?
Like other static methods, we can overload main() in Java. Refer overloading main() in Java for more details.

 `// A Java program with overloaded main() ` `import` `java.io.*; ` ` `  `public` `class` `Test { ` ` `  `    ``// Normal main() ` `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` `        ``System.out.println(``"Hi Geek (from main)"``); ` `        ``Test.main(``"Geek"``); ` `    ``} ` ` `  `    ``// Overloaded main methods ` `    ``public` `static` `void` `main(String arg1) ` `    ``{ ` `        ``System.out.println(``"Hi, "` `+ arg1); ` `        ``Test.main(``"Dear Geek"``, ``"My Geek"``); ` `    ``} ` `    ``public` `static` `void` `main(String arg1, String arg2) ` `    ``{ ` `        ``System.out.println(``"Hi, "` `+ arg1 + ``", "` `+ arg2); ` `    ``} ` `} `

Output :

```Hi Geek (from main)
Hi, Geek
Hi, Dear Geek, My Geek
```

Unlike C++, Java doesn’t allow user-defined overloaded operators. Internally Java overloads operators, for example, + is overloaded for concatenation.

• Overloading is an example of compiler time polymorphism and overriding is an example of run time polymorphism.

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