Writing Methods

Let's write methods to represent the behaviors of the class.

Methods

The behaviors that have been identified are implemented by writing methods for the class.

Some methods are internal to the class and external classes should not be able to call them. In these cases, the methods might be private.

Some methods will need to be called by external classes. In these cases, the methods might be public. The use of public is not necessary if the classes are in the same package.

Methods have a return type.

• If the method is performing an action, but not producing a value, the return type is void.
• If the method is producing a value, the return type will be the type of this value.
• Methods only have one return type. So if you want to return more than one value, you could create a new type in the form of a record.

Accessor Methods

This type of method allows the object to obtain a copy of the value of class or instance variables. These methods will have a return type that is the type of the variable it is returning.

General Format

Dice Class Example

Mutator Methods

This type of method allows the object to modify the public instance variables. These methods will have a return type of void and will take a parameter tha is the new value.

General Format

Dice Class Example

Foldi

Use these images to create a helpful guide for creating a class.

• Print these two images back to back.
• Fold in half along the vertical line.
• Cut along the horizontal lines between the terms and definitions of the terms.

Outside of the Foldi

Inside of the Foldi

Dice Class Code

Either use the Java Playground or an IDE to demonstrate this code to simulate rolling a die.

Use the Java Playground

• Predict the output from running the body of main for testing.
• Run the code to determine if your prediction was correct.
• To the main:
  • add statements to call the accessor method and print the number of sides.
  • add a statement to change the number of sides to 10.
  • add statements to roll the dice and print the value.
  • add a statement to use the toString method.
• Run the code to test the additions you have mad to main

Use an IDE

If you are using an IDE, create two .java files:

• Dice.java
• DiceTester.java

Copy code into the associated .java file.

Your Turn

	Grab a Piece of Paper, Let's Try It!
	In the prior tutorial, you were asked to find an object to model and create a diagram of the class. This could be an object from a game or something physical in your environment. If you can't think of something, consider a spinner or playing card. Implement this class. Create test class to test your class. Create an object of the class and call the methods on this object.