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/* 目的：分析一下单例设计模式中，懒汉式与饿汉式在多线程中的不同！
开发时我们一般选择饿汉式，因为它简单明了，多线程中不会出现安全问题！
而饿汉式需要我们自己处理程序中存在的安全隐患，但是饿汉式的程序技术含量更高！
*//* class SinglePerson implements Runnable{ private static SinglePerson ss = new SinglePerson("hjz", 22);//恶汉式
private int age;
private String name;
private int count;
private SinglePerson(String name, int age){
this.age = age;
this.name = name;
}
private SinglePerson(){
age = 10;
name = " ";
}
public static SinglePerson getInstance(){
return ss;
}
public String getName(){
return name;
}
public int getAge(){
return age;
}
public void setIntroduceCount(){
++count;
}
public int getIntroduceCount(){
return count;
}
public synchronized void run(){
ss.setIntroduceCount();
try{
Thread.sleep(20);
}catch(InterruptedException e){
}
System.out.println("this is " + ss.getName() + " " + ss.getAge() + " 被介绍的次数是：" + ss.getIntroduceCount());
}
} */ class SinglePerson implements Runnable{
private static SinglePerson ss = null;//懒汉式
private int age;
private String name;
private int count;
private SinglePerson(String name, int age){
this.age = age;
this.name = name;
count=0;
}
private SinglePerson(){
age = 10;
name = " ";
}
/*public static SinglePerson getInstance(){
if(ss==null){//单例设计模式中，懒汉式在多线程中的缺憾啊！可能不能保证对象的唯一性
try{
Thread.sleep(10);
}catch(InterruptedException e){}
ss = new SinglePerson("hjz", 22);
}
return ss;
}*/
/* public static synchronized SinglePerson getInstance(){//保证了对象的唯一性，也就是安全性保证了！但是每当调用该函数时
if(ss==null){ //都要判断一下同步锁对象，降低了程序的效率！
try{
Thread.sleep(10);
}catch(InterruptedException e){}
ss = new SinglePerson("hjz", 22);
}
return ss;
} */
public static SinglePerson getInstance(){//这就是懒汉式的安全又效率的代码！
if(ss==null){//这一句是必须判断的！
synchronized(SinglePerson.class){//这一句只是其他的线程访问时判断
if(ss==null){
try{
Thread.sleep(10);
}catch(InterruptedException e){}
ss = new SinglePerson("hjz", 22);
}
}
}
return ss;
}
public String getName(){
return name;
}
public int getAge(){
return age;
}
public void setIntroduceCount(){
++count;
}
public int getIntroduceCount(){
return count;
}
public synchronized void run(){
ss.setIntroduceCount();
System.out.println("this is " + ss.getName() + " " + ss.getAge() + " 被介绍的次数是：" + ss.getIntroduceCount());
}
}class OtherThread extends Thread{
public void run(){
SinglePerson.getInstance().run();
}
}public class Test{
public static void main(String[] args){
new OtherThread().start();
new OtherThread().start();
new OtherThread().start();
new Thread(SinglePerson.getInstance()).start();
}
} |
本文转自 小眼儿 博客园博客，原文链接：http://www.cnblogs.com/hujunzheng/p/3876539.html，如需转载请自行联系原作者