CSE 115

COMMUNICATION TASK

TUTORIAL#2-CALLING METHODS AND PARAMETERS

PATEL VIRALKUMAR ASHOKBHAI.

 

v Calling methods

 

Ø  Method: Method is a java code that tells the object what to do.

 

                                Object has properties and capabilities. Using methods we can tell the object or send the message to the object to perform a particular task. We can imagine a calculator .It’s color, size, shape and all things that describe it are included in its properties. But the actions like addition, subtraction, division, multiplication, finding square root, storage of result in the memory are all its capabilities .These actions are similar to methods in Java.

                            

                                 A constructor is a special method which creates an instance of a class. It initializes the object’s capabilities. It sets the initial stage of the object. If the user does not define any constructor the Java automatically defines a constructor which is called the default constructor.

 

Ø Constructor definition:

               1. Constructor Header:

                     public identifier ( )

                    Here identifier must have the same name as the name of class.

   

              2. Constructor Body: It is always enclosed in curly braces. The collection of               

                   statements between the braces is called a block.

 

            package vehicles;

                public class Car {

                 public Car ( ) {

                 }
            }       

 

 There are other methods also which are different from the constructor.

 The method definition consists of the two things:

     i.  Method Header

     ii. Method Body

 

i. Method Header:

        visibility returntype methodname ( )

Here visibility is a key word which is usually ‘public’.

Method name is usually in lower case but if it has multiple words then the subsequent letters are in upper case.

A method may or may not have a return type. If it does not have a return type it is called void (which is a keyword).*

i. Method Body:

It is always enclosed in curly braces.

 

Consider the example given below.

           public class Stars {

                   public Stars ( ) {

                                           }

                                public void firstmethod ( ) {

                                           }

                                public void secondmethod ( ) {

                                           }

          }

In the above example we have created two methods namely firstmethod and secondmethod and both these methods have no return type. So we have written ‘void’ in the place of return type.             

Ø Syntax of method call:

Objectname.methodname ( );

A method gets its input from the information we pass in the argument list (between the parenthesis).Expressions, variables, or values can be passed as arguments in the argument list. There are same numbers of arguments in the method call as well as method definition. If the parenthesis is empty, then it indicates that the method does not have any arguments. By calling a method we actually invoke or activate a particular capability of that object.

Example: 1

              public void showScore ( );

In the above example we have created a method which calculates and displays the score but before passing this information (code) one should define what does this method do.

Example: 2

              public void convertTemperature ( );

This method converts temperature from one unit to another.

* The constructor method does not have a return type.

 

Calling constructor:

new constructorname ( );

Example: 1

      new star.Supernova ( );

Here the name of the constructor is star.Supernova. The name of the constructor should

be the same as the name of the class.

 

v Parameters and Arguments:

There are actual parameters and formal parameters .Both of them is slightly different from one another.

1. Formal parameters:

During method definition the variables which are used are called the formal parameters.

Example: public void draw(Circle circle) {

                  }

Parameters in the above example are called the formal parameters.

2. Actual parameters:

While invoking a method by calling a method the parameters which are passed into the method are called the actual parameters (arguments).

Example:  d.draw (circle);

Parameter in the above example is the actual parameter.