JAVA利用多线程锁机制实现银行账户存取款线程安全------JAVA

悠悠 2024-03-22 12:34 42阅读 0赞

>     public class BankTest
>     {
>         static Bank b = null;
>         static Bank b1 = null;
>         public static void main(String[] args)
>         {
>             Thread t = new Thread()
>             {
>                 public void run()
>                 {
>                     b = Bank.getBank();
>                 }
>             };
>             Thread t1 = new Thread()
>             {
>                 public void run()
>                 {
>                     b1 = Bank.getBank();
>                 }
>             };
>             t.start();
>             t1.start();
>             try
>             {
>                 t.join();
>             }
>             catch (InterruptedException e)
>             {
>                 throw new RuntimeException(e);
>             }
>             try
>             {
>                 t1.join();
>             }
>             catch (InterruptedException e)
>             {
>                 throw new RuntimeException(e);
>             }
>             System.out.println(b);
>             System.out.println(b1);
>             System.out.println(b == b1);
>         }
>     }
>     
>     class Bank
>     {
>         private Bank(){}
>         private static Bank instance;
>         //方式1
>     //    public static synchronized Bank getBank()
>     //    {
>     //        if(instance == null)
>     //        {
>     //            try
>     //            {
>     //                Thread.sleep(5000);
>     //            }
>     //            catch (InterruptedException e)
>     //            {
>     //                throw new RuntimeException(e);
>     //            }
>     //            instance = new Bank();
>     //        }
>     //        return instance;
>     //    }
>         //方式2
>     //    public static Bank getBank()
>     //    {
>     //        synchronized(Bank.class)
>     //        {
>     //            if(instance == null)
>     //            {
>     //                try
>     //                {
>     //                    Thread.sleep(5000);
>     //                }
>     //                catch (InterruptedException e)
>     //                {
>     //                    throw new RuntimeException(e);
>     //                }
>     //                instance = new Bank();
>     //            }
>     //        }
>     //        return instance;
>     //    }
>         public static Bank getBank()
>         {
>             if(instance == null)
>             {
>                 synchronized (Bank.class) {
>                     if (instance == null) {
>                         try {
>                             Thread.sleep(5000);
>                         } catch (InterruptedException e) {
>                             throw new RuntimeException(e);
>                         }
>                         instance = new Bank();
>                     }
>                 }
>             }
>             return instance;
>         }
>     }
> 
> public class BankTest  
> \{  
> static Bank b = null;  
> static Bank b1 = null;  
> public static void main(String\[\] args)  
> \{  
> Thread t = new Thread()  
> \{  
> public void run()  
> \{  
> b = Bank.getBank();  
> \}  
> \};  
> Thread t1 = new Thread()  
> \{  
> public void run()  
> \{  
> b1 = Bank.getBank();  
> \}  
> \};  
> t.start();  
> t1.start();  
> try  
> \{  
> t.join();  
> \}  
> catch (InterruptedException e)  
> \{  
> throw new RuntimeException(e);  
> \}  
> try  
> \{  
> t1.join();  
> \}  
> catch (InterruptedException e)  
> \{  
> throw new RuntimeException(e);  
> \}  
> System.out.println(b);  
> System.out.println(b1);  
> System.out.println(b == b1);  
> \}  
> \}
> 
> class Bank  
> \{  
> private Bank()\{\}  
> private static Bank instance;  
> //方式1  
> // public static synchronized Bank getBank()  
> // \{  
> // if(instance == null)  
> // \{  
> // try  
> // \{  
> // Thread.sleep(5000);  
> // \}  
> // catch (InterruptedException e)  
> // \{  
> // throw new RuntimeException(e);  
> // \}  
> // instance = new Bank();  
> // \}  
> // return instance;  
> // \}  
> //方式2  
> // public static Bank getBank()  
> // \{  
> // synchronized(Bank.class)  
> // \{  
> // if(instance == null)  
> // \{  
> // try  
> // \{  
> // Thread.sleep(5000);  
> // \}  
> // catch (InterruptedException e)  
> // \{  
> // throw new RuntimeException(e);  
> // \}  
> // instance = new Bank();  
> // \}  
> // \}  
> // return instance;  
> // \}  
> public static Bank getBank()  
> \{  
> if(instance == null)  
> \{  
> synchronized (Bank.class) \{  
> if (instance == null) \{  
> try \{  
> Thread.sleep(5000);  
> \} catch (InterruptedException e) \{  
> throw new RuntimeException(e);  
> \}  
> instance = new Bank();  
> \}  
> \}  
> \}  
> return instance;  
> \}  
> \}