exercise9_5.java

Introduction to java programming 一书中所有编程练习部分的源码

/*
 * Exercise9_5.java
 *
 * Created on September 17, 2002, 2:34 PM
 */

/**
 *
 * @author  administrator
 */
public class Exercise9_5 {
  public static void main(String[] args) {
    Circle9_5 obj1 = new Circle9_5();
    Circle9_5 obj2 = new Circle9_5();
    
    System.out.println(obj1);  
    System.out.println(obj2);  
    System.out.println(obj1.equals(obj2));  
    System.out.println(obj1.compareTo(obj2));  
  }
}

// Circle.java: The circle class that extends GeometricObject
class Circle9_5 extends GeometricObject implements Comparable {
  private double radius;

  /** Default constructor */
  public Circle9_5() {
    this(1.0);
  }

  /** Construct circle with a specified radius */
  public Circle9_5(double radius) {
    this(radius, "white", false);
  }

  /** Construct a circle with specified radius, filled, and color */
  public Circle9_5(double radius, String color, boolean filled) {
    super(color, filled);
    this.radius = radius;
  }

  /** Return radius */
  public double getRadius() {
    return radius;
  }

  /** Set a new radius */
  public void setRadius(double radius) {
    this.radius = radius;
  }

  /** Implement the findArea method defined in GeometricObject */
  public double findArea() {
    return radius * radius * Math.PI;
  }

  /** Implement the findPerimeter method defined in GeometricObject*/  
  public double findPerimeter() {
    return 2 * radius * Math.PI;
  }

  /** Override the toString() method defined in the Object class */
  public String toString() {
    return "[Circle] radius = " + radius;
  }
  
  public int compareTo(Object obj) {
    if (this.findArea() > ((Circle9_5)obj).findArea())
      return 1;
    else if (this.findArea() < ((Circle9_5)obj).findArea())
      return -1;
    else
      return 0;
  }
  
  public boolean equals(Object obj) {
    return this.radius == ((Circle9_5)obj).radius;
  }
}