（单例设计模式中）懒汉式与饿汉式在多线程中的不同

/*
 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();
    }
}