How to define a method

A method is a programmed procedure that is defined as part of a class. A class (and thus an object) can have more than one method.

Syntax of method definition

    modifier returnType methodName(parameters) Exception List{

        Method Body

    }

Method definition composed of six components :

modifiers : like private, public, protected or default. We have already seen private, public and default. Will discuss more about these in the packages section.

ReturnType : The type of the value written by the method. If you don't want to return any value make the return type as void. Return type will be any primitive type or reference type.

MethodName : The name given to the method

parameters: Method is defined with parameters or with out parameters. A method can be defined with any number of parameters.

Exception List: A Method can throw any number of exceptions, will discuss about this on ExceptionHandling section

Method Body: The actual implementation of the method goes here

Example

    1. public int sum(int a, int b){

        return (a+b);

        }

        modifier : public

        returnType : int

        methodName : sum

        parameters : a,b

        Exception List : none

        Method body : calculates the sum of the two parameters and return the sum.

2. void sayHello(){

        System.out.println(“Hello”);

    }

    modifier : default

    returnType : void

    methodName : sayHello

    parameters :none

    Exception List : none

    Method body : simply prints the message “Hello” to the console.

If no access specifier (modifier) specified to a variable or method, it assumes default access specifier(modifier).

Naming a Method

By convention method names starts with a small character and starting character of subsequent words is capitalized.

    Example:

    walk()

    sleep()

    setColor(String s)

    getHeight()

Local Variables

Variables declared inside a method are called local variables. These are not accessible out side of the method. You must initialize local variables before using.

Some Points to remember

Trying to use local variables before initializing causes compile time error

Example

class LocalVariable{
 int sum(int a, int b){
  int c;
  System.out.println(c);
  return (a+b);
 }
} 

Since “c” is a local variable, when your program tries to access local variable, before initialization, compiler will throw the error.

 

For the above program, you will get below error
LocalVariable.java:5: error: variable c might not have been initialized
            System.out.println(c);
                                          ^
1 error

Instance methods                                                 More about methods                                                 Home