Polymorphism in Java : Override Polymorphism « Class « Java

1. Java
2. Class
3. Override Polymorphism

Polymorphism in Java

// : c07:Shapes.java
// Polymorphism in Java.
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.

import java.util.Random;

class Shape {
  void draw() {
  }

  void erase() {
  }
}

class Circle extends Shape {
  void draw() {
    System.out.println("Circle.draw()");
  }

  void erase() {
    System.out.println("Circle.erase()");
  }
}

class Square extends Shape {
  void draw() {
    System.out.println("Square.draw()");
  }

  void erase() {
    System.out.println("Square.erase()");
  }
}

class Triangle extends Shape {
  void draw() {
    System.out.println("Triangle.draw()");
  }

  void erase() {
    System.out.println("Triangle.erase()");
  }
}

// A "factory" that randomly creates shapes:

class RandomShapeGenerator {
  private Random rand = new Random();

  public Shape next() {
    switch (rand.nextInt(3)) {
    default:
    case 0:
      return new Circle();
    case 1:
      return new Square();
    case 2:
      return new Triangle();
    }
  }
}

public class ShapesDemo {
  private static RandomShapeGenerator gen = new RandomShapeGenerator();

  public static void main(String[] args) {
    Shape[] s = new Shape[9];
    // Fill up the array with shapes:
    for (int i = 0; i < s.length; i++)
      s[i] = gen.next();
    // Make polymorphic method calls:
    for (int i = 0; i < s.length; i++)
      s[i].draw();

  }
} ///:~



           
       

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