Ensuring proper cleanup : Finalize « Language Basics « Java

1. Java
2. Language Basics
3. Finalize

Ensuring proper cleanup

// : c06:CADSystem.java
// Ensuring proper cleanup.
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.


class Shape {
  Shape(int i) {
    System.out.println("Shape constructor");
  }

  void dispose() {
    System.out.println("Shape dispose");
  }
}

class Circle extends Shape {
  Circle(int i) {
    super(i);
    System.out.println("Drawing Circle");
  }

  void dispose() {
    System.out.println("Erasing Circle");
    super.dispose();
  }
}

class Triangle extends Shape {
  Triangle(int i) {
    super(i);
    System.out.println("Drawing Triangle");
  }

  void dispose() {
    System.out.println("Erasing Triangle");
    super.dispose();
  }
}

class Line extends Shape {
  private int start, end;

  Line(int start, int end) {
    super(start);
    this.start = start;
    this.end = end;
    System.out.println("Drawing Line: " + start + ", " + end);
  }

  void dispose() {
    System.out.println("Erasing Line: " + start + ", " + end);
    super.dispose();
  }
}

public class CADSystem extends Shape {
  private Circle c;

  private Triangle t;

  private Line[] lines = new Line[5];

  public CADSystem(int i) {
    super(i + 1);
    for (int j = 0; j < lines.length; j++)
      lines[j] = new Line(j, j * j);
    c = new Circle(1);
    t = new Triangle(1);
    System.out.println("Combined constructor");
  }

  public void dispose() {
    System.out.println("CADSystem.dispose()");
    // The order of cleanup is the reverse
    // of the order of initialization
    t.dispose();
    c.dispose();
    for (int i = lines.length - 1; i >= 0; i--)
      lines[i].dispose();
    super.dispose();
  }

  public static void main(String[] args) {
    CADSystem x = new CADSystem(47);
    try {
      // Code and exception handling...
    } finally {
      x.dispose();
    }

  }
} ///:~



           
       

Related examples in the same category

1.	Using finalize() to detect an object that hasn't been properly cleaned up
2.	Demonstrate how finalize() methods and shutdownHooks interact