（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();
	}
}

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