Java Singleton mode (thread safe, high efficiency, double inference)

Such a method, when acquiring simple interest, avoids the thread lock, which leads to an interview that the method is very slow,
The same is, prevent multi-threaded colleague House This method will produce multiple instances of the problem.

High efficiency. Thread safety.

public class testinstance{
private static testinstance instance;
public static Testinstance getinstance{
IfInstance==null){
Synchronized (Testinstance.class){if (Instance==null){
Instance=new testinstance ();
}
}
ReturnInstance
}

}



}

Java Singleton mode (thread safe, high efficiency, double inference)