Interface: Interface is a reference type in Java, which contains a collection of abstract methods. An interface needs to the follow certain conditions such as: One cannot instantiate an interface. Interfaces do not contain any constructors. All methods present in the interface are abstracts. An interface does not contain any instance field. An interface cannot be extended by a class. Comparable Interface : A comparable interface is a generic interface that defines the compareTo() method that is used for comparing objects. Using comparable interface, one can choose the properties of the objects, rather than the reference location of the objects. Example: //java langauage package for comaprable interface package java.lang //comparable interface definition public interface Comparable <E> { //use of compareTo to compare objects public integer compareTo(E o); } Explanation: The compareTo() method determines the order of this object with the specified object “o” and returns a negative integer, zero or positive integer, if this object is less than, equal to or greater than object “o”.

Question

Modified Circle class and test file: Add a new attribute for color (or any other new attribute) Add get/set methods for this new instance variable, including data validation in set method (assuming background is black, i.e. circle color can't be black, reset to any non-black color if black is entered ). Add a new constructor to pass the color attribute as an argument. Add an instance method to display all properties of a Circle object. Create 2 objects using different constructors in test file, with invalid data. Use this test java file test java file: class CircleTest{ public static void main(String[] args){ int num = 10; Circle c1 = new Circle(0.001); Circle c2 = new Circle("black", -9); c1.display(); c2.display(); c1.setRadius( -1); c1.setColor("black"); c1.display(); }}

Answer 1

Question

Chapter 13.6, Problem 13.6.1CP

Program Plan Intro

Interface:

Interface is a reference type in Java, which contains a collection of abstract methods.

An interface needs to the follow certain conditions such as:

One cannot instantiate an interface.

Interfaces do not contain any constructors.

All methods present in the interface are abstracts.

An interface does not contain any instance field.

An interface cannot be extended by a class.

Comparable Interface:

A comparable interface is a generic interface that defines the compareTo() method that is used for comparing objects.

Using comparable interface, one can choose the properties of the objects, rather than the reference location of the objects.

Example:

//java langauage package for comaprable interface

package java.lang

//comparable interface definition

public interface Comparable <E>

{

//use of compareTo to compare objects

public integer compareTo(E o);

}

Explanation:

The compareTo() method determines the order of this object with the specified object “o” and returns a negative integer, zero or positive integer, if this object is less than, equal to or greater than object “o”.

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