testinterface.java

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// TestInterface.java: 使用接口:Comparable 
// 使用Max类中的max()方法, 寻找最大的对象

public class TestInterface
{
  // Main method
  public static void main(String[] args)
  {
    // Create two comarable circles
    ComparableCircle circle1 = new ComparableCircle(5);
    ComparableCircle circle2 = new ComparableCircle(4);

    // Display the max circle
    Comparable circle = Max.max(circle1, circle2);
    System.out.println("The max circle's radius is " +
      ((Circle)circle).getRadius());
    System.out.println(circle);

    // Create two comarable cylinders
    ComparableCylinder cylinder1 = new ComparableCylinder(5, 2);
    ComparableCylinder cylinder2 = new ComparableCylinder(4, 5);

    // Display the max cylinder
    Comparable cylinder = Max.max(cylinder1, cylinder2);
    System.out.println();
    System.out.println("cylinder1's volume is " +
      cylinder1.findVolume());
    System.out.println("cylinder2's volume is " +
      cylinder2.findVolume());
    System.out.println("The max cylinder's \tradius is " +
      ((Cylinder)cylinder).getRadius() + "\n\t\t\tlength is " +
      ((Cylinder)cylinder).getLength() + "\n\t\t\tvolume is " +
      ((Cylinder)cylinder).findVolume());
    System.out.println(cylinder);
  }
}

// ComparableCircle is a subclass of Circle, which implements the
// Comparable interface
class ComparableCircle extends Circle implements Comparable
{
  // Construct a CompareCircle with specified radius
  public ComparableCircle(double r)
  {
    super(r);
  }

  // Implement the compareTo method defined in Comparable
  public int compareTo(Object o)
  {
    if (getRadius() > ((Circle)o).getRadius())
      return 1;
    else if (getRadius() < ((Circle)o).getRadius())
      return -1;
    else
      return 0;
  }
}

// ComparableCylinder is a subclass of Cylinder, which implements the
// CompareObject interface
class ComparableCylinder extends Cylinder implements Comparable
{
  // Construct a CompareCylinder with radius and length
  ComparableCylinder(double r, double l)
  {
    super(r, l);
  }

  // Implement the compareTo method defined in Comparable interface
  public int compareTo(Object o)
  {
    if (findVolume() > ((Cylinder)o).findVolume())
      return 1;
    else if (findVolume() < ((Cylinder)o).findVolume())
      return -1;
    else
      return 0;
  }
}