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Last Minute Java Method Signature and Rules Explained Tutorial

Java Method Signature Rules Explained

A Java Class consists of a number of Methods. These methods help us in Code Reuse. These methods are similar to the Functions in C language. Let us know more about Java Method Signature, Naming convention and usage.

Note: All Java methods are written inside a Java Class.

Java Method Signature and Rules Explained

Java Method Signature is nothing but a combination of Return-Type, Method's Name and a Parameter list it accepts.

The method signature or syntax is as follows.

type METHODNAME(type param1, type param2..)
{
  //statements
  //..
  //return statement
}

Let us know about parts of Java Method Signature.

  1. Return Type
  2. Method Name
  3. Parameter List

1. Return Type: A Java method may or may not return a value. If it returns nothing, we specify it explicitly mentioning a "void" before it. A method can return primitive or Object type values.

2. Method Name: A Java Method Name can be a combination of Alphabets, Numbers and Special Symbols (Underscore and Dollar only).

Java Method Naming Rules:

  • Method name can start with a Letter or Alphabet.
  • Method name can start with either Underscore(_) or Dollar($) symbol.
  • Method name can not start with a number.
  • Method name can contain numbers in-between or at the end.
  • Method name can not be a keyword.
  • Method name can be the same as the name of Class but it is not recommended.

3. Parameter List: Java methods can contain any number of parameters of any type. There can be zero parameters also. Variables which are part of a Parameter-list are also called Local Variables. Local variables are stored in Stack Memory. Also, the variables declared inside a method are also called Local Variables or Method Variables.

Naming Conventions or Rules for Local Variables:

  • Name of a Local variable can start with an Alphabet lowercase or uppercase. Lowercase is preferred.
  • Name of a Local variable can start with either an Underscore(_) or Dollar($) symbol.
  • Name of a Local variable can not start with a number but it can contain numbers in-between or at the end.
  • Name can not be a keyword.
  • No two Local variables should have the same name.
  • A Local variable can not be used without initializing if it is not part of the parameter list.

An example Java program below explains how to pass arguments to a Java method and return values or objects from a method.

class Table
{
  int height;
}

public class JavaMethodExample
{	
  public static void main(String[] args)
  {
    JavaMethodExample je = new JavaMethodExample();
    Table t1 = new Table();
    t1.height = 10;
    je.show(t1); //Passing arguments to method

    int changedValue = je.increase(t1);
    System.out.println("New Height= " + changedValue);
    //System.out.println("New Height= " + t1.height); //This code also works
  }

  void show(Table tab) //Receiving parameters in method
  {
    System.out.println("Height= " + tab.height);
  }

  int increase(Table tab) //Returning a value
  {
    tab.height = tab.height + 20;
    return tab.height;
  }	

}
//OUTPUT
//Height= 10
//New Height= 30

In the above example, the method "show" receives parameters. The method "increase" receives an object reference as a parameter and returns an integer value back to the calling method. Remember that "main" is also a method which is the starting point of program execution.

This is how Java Methods are defined and used following Method Signature rules. Using a lower case first letter is a convention followed by good Java programmers.

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