深入JVM之号称世界上所有Java程序员都会犯的一个错误

package com.jadyer.classloader;

/**
 * 深入JVM之号称世界上所有Java程序员都会犯的一个错误
 * @author 宏宇
 * @editor Jan 24, 2012 7:49:18 PM
 * @see 这是一个很无耻的面试题，多么卑鄙的人才能写出这种自己给自己找麻烦的代码啊~~
 */
public class ClassLoadTest {
	public static void main(String[] args) {
		SingletonFront singletonFront = SingletonFront.getInstance();
		System.out.println("counter11 = " + singletonFront.counter11);
		System.out.println("counter22 = " + singletonFront.counter22);
		System.out.println("=============");
		SingletonBack singletonBack = SingletonBack.getInstance();
		System.out.println("counter33 = " + singletonBack.counter33);
		System.out.println("counter44 = " + singletonBack.counter44);
	}
}

/**
 * 单例类：在变量之前new的实例
 * @see Step01:为静态变量分配内存并初始化为默认值
 * @see 	   singletonFront=null,counter11=0,counter22=0
 * @see Step02:为静态变量赋正确的初始值，并初始化类的实例
 * @see		   singletonFront=new SingletonFront(),counter11=1,counter22先因为构造方法等于壹之后又因为初始值等于零
 */
class SingletonFront{
	private static SingletonFront singletonFront = new SingletonFront(); //注意这个位置
	public static int counter11;
	public static int counter22 = 0;
	private SingletonFront(){
		counter11++;
		counter22++;
	}
	public static SingletonFront getInstance(){
		return singletonFront;
	}
}

/**
 * 单例类：在变量之后new的实例
 * @see Step01:为静态变量分配内存并初始化为默认值
 * @see 	   counter11=0,counter22=0,singletonFront=null
 * @see Step02:为静态变量赋正确的初始值，并初始化类的实例
 * @see		   counter11与counter22都是先等于零之后又因为构造方法才等于壹,singletonFront=new SingletonFront()
 */
class SingletonBack{
	public static int counter33;
	public static int counter44 = 0;
	private static SingletonBack singletonBack = new SingletonBack(); //注意这个位置
	private SingletonBack(){
		counter33++;
		counter44++;
	}
	public static SingletonBack getInstance(){
		return singletonBack;
	}
}