Singleton and static

 

The constructor of The Singleton is private and the object cannot be created directly with new. Although static can be used at any time, it is still possible to be re-created.

For example, you want to have an instance of Class A at any time.
Class B {
Static A = new ();
}
In this way, you can use B. A to call the method in.

But it may be in class C.
Class C {
Public void geta {
A A = new ();
}
}

At this time, two objects of a appear in the whole project, which is contrary to your original design. In the future, there may be more people new ();

If you design a as a singleton at the time, there will be no such embarrassing situation.