多线程情况下的单例模式创建

public class SingletonTest { 
 
    private static SingletonTest instance = null; 
 
    private SingletonTest() { 
    } 
 
    private static synchronized void syncInit() { 
        if (instance == null) { 
            instance = new SingletonTest(); 
        } 
    } 
 
    public static SingletonTest getInstance() { 
        if (instance == null) { 
            syncInit(); 
        } 
        return instance; 
    } 
}