gymchua_2.java

package _3;

import java.util.*;

public class Test {
  public static void main(String[] args) {
    Shape s = new Rectangle(3, 4, "white");
    System.out.println(s.toString());
    System.out.println("Area = " + s.getArea());

    s = new Triangle(4, 5, "black");
    System.out.println(s.toString());
    System.out.println("Area = " + s.getArea());
  }
}

public abstract class Shape {
  protected String color;

  //
  // Constructor
  //

  public Shape() {
    this.color = "";
  }

  public Shape(String color) {
    this.color = color;
  }

  public abstract double getArea();

  //
  // Getter & setter
  //

  public String getColor() {
    return this.color;
  }

  public void setColor(String color) {
    this.color = color;
  }
}

public class Rectangle extends Shape {
  private double length;
  private double width;

  public Rectangle() {
    super();
    this.length = 0;
    this.width = 0;
  }

  public Rectangle(double length, double width, String color) {
    this.length = length;
    this.width = width;
    super(color);
  }

  @Override
  public double getArea() {
    return this.length * this.width;
  }

  public double getPerimeter() {
    return 2.0 * (this.length + this.width);
  }

  public String toString() {
    return "Rectangle{length=" + length +
           ", width=" + width +
           ", color=" + color + "}";
  }
}

public class Triangle extends Shape {
  private double base;
  private double height;

  public Triangle() {
    super();
    this.base = 0;
    this.height = 0;
  }

  public Triangle(double base, double height, String color) {
    super(color);
    this.base = base;
    this.height = height;
  }

  public double getArea() {
    return 0.5 * this.base * this.height;
  }

  public String toString() {
    return "Triangle{base=" + base +
           ", height=" + height +
           ", color=" + color + "}";
  }
}