//: reusing/CADSystem.java

// Ensuring proper cleanup.

package reusing;

class Shape{

Shape(int i){

System.out.println("Shape construstor");

}

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");

}

}

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[3];

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 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 { // 保护区

// Code and exception handling...

// 特殊处理

} finally { // finally子句中的代码总是要被执行的

x.dispose();

}

}

}