Chapter 21- Using Generics Case Study: Geometric Bunch

Chapter 21- Using Generics – Case Study: Geometric Bunch

In this example a class called GeometricBunch is made to wrap around a list of GeometricObjects. Circle and Rectangle are subclasses of GeometricObject. The subclasses are comparable. The wrapper includes three methods: showList(), findLocationElementWithLargestArea(), and sortElements()

Class: Driver

package csu.matos;

import java.util.ArrayList;

public class Driver {

/**

* Author: V. Matos

* Date: Spring-2012

* Goal: Various code fragments to demonstrate issues on

* Java Generics - Chapter 21.

public static void main(String[] args) {

TestGeometricBunch test = new TestGeometricBunch();

test.main(null);

}//main

}

Class: TestGeometricBunch

package csu.matos;

/**

* Author: V. Matos

* Date: Spring-2012

* Goal: Generics Case STudy - In this example a class called

* GeometricBunch is made to wrap around a list of GeometricObjects.

* Circle and Rectangle are subclasses of GeometricObject. The

* subclasses are comparable. The wrapper includes three methods:

* showList(), findLocationElementWithLargestArea(), and sortElements()

import java.util.ArrayList;

public class TestGeometricBunch {

public static void main(String[] arg) {

GeometricBunchGeometricObject> bunch = new GeometricBunchGeometricObject>();

Circle c1 = new Circle(1);

Circle c2 = new Circle(2);

Circle c3 = new Circle(3);

bunch.add(c1);

bunch.add(c2);

bunch.add(c3);

Rectangle r1 = new Rectangle(1, 20);

Rectangle r2 = new Rectangle(10, 2);

Rectangle r3 = new Rectangle(10, 0.5);

bunch.add(r1);

bunch.add(r2);

bunch.add(r3);

bunch.showList();

System.out.println("\nLargestArea at " + bunch.getLargest());

ArrayListGeometricObject> list2 = bunch.sortElements();

int i = 0;

for (GeometricObject g : list2) {

String objType = g.getClass().getSimpleName();

System.out

.printf("\n[%d]: %s \t %3.2f ", i++, objType, g.getArea());

}

Class: GeometricObject

package csu.matos;

public abstract class GeometricObject implements Comparable<GeometricObject> {

@Override

public int compareTo(GeometricObject o2) {

double area1 = this.getArea();

double area2 = o2.getArea();

if (area1 < area2)

return -1;

else if (area1 == area2)

return 0;

else

return 1;

}

private String color = "white";

private boolean filled;

private java.util.Date dateCreated;

// Construct a default geometric object

protected GeometricObject() {

dateCreated = new java.util.Date();

}

// create object with color and filled value

protected GeometricObject(String color, boolean filled) {

dateCreated = new java.util.Date();

this.color = color;

this.filled = filled;

}

// Return color

public String getColor() {

return color;

}

// Set a new color

public void setColor(String color) {

this.color = color;

}

// Return TRUE is object is filled

public boolean isFilled() {

return filled;

}

public void setDateCreated(java.util.Date dateCreated) {

this.dateCreated = dateCreated;

}

// Set filled to either: true/false

public void setFilled(boolean filled) {

this.filled = filled;

}

// Get dateCreated

public java.util.Date getDateCreated() {

return dateCreated;

}

// Return a string representing this object

public String toString() {

return " created on " + dateCreated + "\n color: " + color

+ " and filled: " + filled;

}

// Abstract method getArea

public abstract double getArea();

// Abstract method getPerimeter

public abstract double getPerimeter();

}

Class: Rectangle

package csu.matos;

public class Rectangle extends GeometricObject {

private double width;

private double height;

public Rectangle() {

}

public Rectangle(double width, double height) {

this.width = width;

this.height = height;

}

/** Return width */

public double getWidth() {

return width;

}

/** Set a new width */

public void setWidth(double width) {

this.width = width;

}

/** Return height */

public double getHeight() {

return height;

}

/** Set a new height */

public void setHeight(double height) {

this.height = height;

}

/** Return area */

public double getArea() {

return width * height;

}

/** Return perimeter */

public double getPerimeter() {

return 2 * (width + height);

}

public String toString() {

return " > Rectangle " + getColor() + "\n" + super.toString()

+ "\n > Height: " + getHeight() + " Width: " + getWidth()

+ " Perimeter: " + getPerimeter() + " Area: " + getArea();

}

Class: Circle

package csu.matos;

public class Circle extends GeometricObject {

private double radius;

public Circle() {

}

public Circle(double radius) {

this.radius = radius;

}

/** Return radius */

public double getRadius() {

return radius;

}

/** Set a new radius */

public void setRadius(double radius) {

this.radius = radius;

}

/** Return area */

public double getArea() {

return radius * radius * Math.PI;

}

/** Return diameter */

public double getDiameter() {

return 2 * radius;

}

/** Return perimeter */

public double getPerimeter() {

return 2 * radius * Math.PI;

}

/* Print the circle info */

public void printCircle() {

System.out.println("The circle is created " + getDateCreated()

+ " and the radius is " + radius);

}

public String toString() {

return " > Circle " + getColor() + "\n" + super.toString()

+ "\n > Radius: " + getRadius() + " Perimeter: "

+ getPerimeter() + " Area: " + getArea();

}

CONSOLE

[0]: > Circle white

created on Fri Feb 10 12:21:02 EST 2012