Method Signature & Header

1. Method Signature

A method signature in Java uniquely identifies a method. It consists of:

• Method Name

• Parameter List (number, type, and order of parameters)

Return type, access modifiers, and exceptions are NOT part of the method signature.

Example: Method Signatures

void display(int x) { }       // Signature: display(int)
void display(String s) { }    // Signature: display(String)
void display(int x, int y) { } // Signature: display(int, int)

All these methods have different signatures, so method overloading is allowed.

2. Why is Return Type NOT Part of the Signature?

Java does NOT allow method overloading based only on return type because it leads to ambiguity.

int getData() { return 10; }
double getData() { return 10.5; }  // Compilation Error (Same signature: `getData()`)

Even though the return types differ, the method signature remains getData(), leading to a conflict.

2. What is a Method Header?

A method header includes more information than the method signature. It consists of:

• Access Modifiers (public, private, protected, or default)

• Return Type (void, int, String, etc.)

• Method Name

• Parameter List

• Exception List (if the method declares exceptions using throws)

Example: Method Header vs. Method Signature

public int calculateSum(int a, int b) throws IOException { }

• Method Signature: calculateSum(int, int)

• Method Header: public int calculateSum(int a, int b) throws IOException