静态实例变量引用类的实例

Question

Can I let a static field of a class keep a reference to an instance of itself? If so, will it keep alive in the jvm without anyone else keeping a reference?

public class StatTest {
    private static StatTest statTest;

    public static StatTest getStatTest () {
        if (statTest== null) {
            statTest= new StatTest ();
            statTest.init();
        }
        return statTest;
    }

    private StatTest() { }
}

Answer 1

是的，这是Singleton设计模式的概念！

Answer 2

This is one way to create a singleton of a class.

So to answer your question:

• Yes, it is possible
• All references to the getStatTest() method will return that instance.

When using this method for a singleton, the method is mostly called getInstance() =)

Answer 3

will it keep alive in the jvm without anyone else keeping a reference?

Yes, as long as the class itself is not eligible for garbage collection (which can only happen if you use a custom classloader).

Answer 4

Congrats. You've reinvented the singleton. http://en.wikipedia.org/wiki/Singleton_pattern