Java初始化与清理的案例分析

 Object obj = new Object(); // 左侧为声明对象，右侧为实际创建一个对象

package com.thinkinjava.initialization;
import static com.thinkinjava.util.Print.*;

class Tree {
 int height;
 Tree() {
 print("Planting a seedling");
 height = 0;
 }
 Tree(int initialHeight) {
 height = initialHeight;
 print("Creating new Tree that is " +
  height + " feet tall");
 } 
 void info() {
 print("Tree is " + height + " feet tall");
 }
 void info(String s) {
 print(s + ": Tree is " + height + " feet tall");
 }
}

public class Overloading {
 public static void main(String[] args) {
 for(int i = 0; i <5; i++) {
  Tree t = new Tree(i);
  t.info();
  t.info("overloaded method");
 }
 // Overloaded constructor:
 new Tree();
 } 
}

package com.thinkinjava.multiplex;

import static com.thinkinjava.util.Print.print;

/**
 * 初始化顺序
 *
 */

// 形状
class Insect {
  private int i = 9;
  protected int j;
  private int k = priInit("Insect.k initialized");

  Insect() {
    print("i = " + i + ",j = " + j);
    j = 39;
  }

  private static int x1 = priInit("static Insect.x1 initialized");

  static int priInit(String s) {
    print(s);
    return 47;
  }
}

class InitOrder extends Insect {
  private int i = 10;
  private int k = priInit("InitOrder.k initialized");

  public InitOrder() {
    print(" k = " + k);
    print(" j = " + j);
  }

  private static int x2 = priInit("static InitOrder.x2 initialized");

  public static void main(String[] args) {
    print("InitOrder constructor");
    InitOrder x = new InitOrder();
  }
}

import static com.thinkinjava.util.Print.print;

/**
 * 确保正确清理
 * */

// 形状
class Shape {
 Shape(int i) {
 print("Shape constructor");
 }

 // 处理
 void dispose() {
 print("Shape dispose");
 }
}

class Circle extends Shape {
 Circle(int i) {
 super(i);
 print("Circle constructor");
 }

 void dispose() {
 print("Circle dispose");
 super.dispose();
 }
}

// 三角形
class Triangle extends Shape {
 Triangle(int i) {
 super(i);
 print("Triangle constructor");
 }

 void dispose() {
 print("Triangle dispose");
 super.dispose();
 }
}

class Line extends Shape {
 private int start, end;

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

 void dispose() {
 // 擦除线条
 print("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 = 0; i--) {
  lines[i].dispose();
 }
 super.dispose();
 }

 public static void main(String[] args) {
 CADSystem x = new CADSystem(47);
 try {
  // 程序编码与异常处理
 } finally {
  x.dispose();
 }
 }