单例在多线程中保证线程安全

ゝ一世哀愁。 2023-08-17 17:47 202阅读 0赞

在多线程模式中，考虑到性能和线程安全问题，一般选择两种比较经典的单例模式，既能提高性能，也能保证线程安全  
 1、double check instance 双重检查锁定  
    原理参考链接：[双重检查锁定原理链接][Link 1]

public class DubbleSingleton { 
    
    	private volatile static DubbleSingleton ds;
    	
    	public static DubbleSingleton getDs(){ 
    		if(ds == null){ 
    			try { 
    				//模拟初始化对象的准备时间...
    				Thread.sleep(3000);
    			} catch (InterruptedException e) { 
    				e.printStackTrace();
    			}
    			synchronized (DubbleSingleton.class) { 
    				if(ds == null){ 
    					ds = new DubbleSingleton();
    				}
    			}
    		}
    		return ds;
    	}
    	
    	public static void main(String[] args) { 
    		Thread t1 = new Thread(new Runnable() { 
    			@Override
    			public void run() { 
    				System.out.println(DubbleSingleton.getDs().hashCode());
    			}
    		},"t1");
    		Thread t2 = new Thread(new Runnable() { 
    			@Override
    			public void run() { 
    				System.out.println(DubbleSingleton.getDs().hashCode());
    			}
    		},"t2");
    		Thread t3 = new Thread(new Runnable() { 
    			@Override
    			public void run() { 
    				System.out.println(DubbleSingleton.getDs().hashCode());
    			}
    		},"t3");
    		
    		t1.start();
    		t2.start();
    		t3.start();
    	}
    	
    }

2. static inner class 静态内部类模式

public class InnerSingleton { 
    	
    	private static class Singletion { 
    		private static Singletion single = new Singletion();
    	}
    	
    	public static Singletion getInstance(){ 
    		return Singletion.single;
    	}
    	
    }

[Link 1]: https://www.cnblogs.com/zhuifeng523/p/11360012.html