Mega Code Archive
Ensuring proper cleanup
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// : 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();
}
}
} ///:~
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