How to use Methods in Java.

#Topic-9

Previous topic (8) we have discussed about what is Class, Constructors and this keyword in Java.  

If you have not gone through that topic, click this link Class, Constructors and this keyword in Java.

In this section we will discuss about How to use Methods in Java.

Method:

Method is a collection of statements that are grouped together to perform an operation.

System.out.println() – it is a method, it execute several statement in order to display a message(internally).

Two types:

1. Methods which does not return value

2. Methods which have return value

1. Methods which does not return value:

It must proceeded by void keyword.

2. Methods which return value:

It has 2 types:

a) Methods which have parameters

b) Methods which do not have parameters

a) Methods which have parameters:

We can avoid creation of constructor in order to use parameterized method provide values ,We have to create multiple objects. 
Note: Don’t assign any values to parameters variable (not a good practice)

Example:

Cal c=new Cal();

c.add(10,20);

Cal c1=new Cal();

c1.add(30,40);

b) Methods which do not have parameters

It doesn’t contain any parameters.

2. Methods which have return value:

Methods can return only one value at a time; a method can return primitive value, array and object. It must contain a return statement.

Note: after return() statement should not write anything. If we write anything after return statement compilation error will occur like un-reachable code.

Method Overloading / compile time polymorphism.

Method overloading can be achieved based on differ from the number of parameters, data type of each parameter and sequence of parameter data type. Method name should be same.

It also called as compile time polymorphism, static binding and early binding.

Note:

·        Based on the return type we cannot overload the method.

·        We can overload main method also.

Difference between Constructor and Method

sl.no	Java Constructor	Java Method
1	Constructor is used to initialize the state of an object.	Method is used to expose behavior of an object.
2	Constructor must not have return type.	Method must have return type.
3	Constructor is invoked implicitly.	Method is invoked explicitly.
4	The java compiler provides a default constructor if you don't have any constructor.	Method is not provided by compiler in any case.
5	Constructor name must be same as the class name.	Method name may or may not be same as class name.

 

What is Next?
In the next section, we will be going through Call by Value and Call by reference.
 

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