Java Singleton class/

Java Singleton class

A class can only create one instance, then this class is a singleton class

　　

You can override the ToString method to output what you want to output

You can override equcal to compare whether the content you want to compare is equal

cannot be re-assigned to a final decorated member variable if it has an initial value

The static modified member variable can specify an initial value in a static code block or when declaring the member

Instance members can declare an attribute in a non-static code block, or specify an initial value in the constructor

The final modified variable must be displayed for initialization

The final modifier reference variable cannot be re-assigned but can change the content of the referenced object (as long as the address value is unchanged)

The final modified method cannot be overridden

The final decorated class cannot have subclasses so a class that does not want to be inherited can be declared final.

Java Singleton class/