Another usage of java Array

Another usage of java Array

You can easily use an enum to build a singleton or tool class.

Import java. io. Serializable; public enum SafeSingleton implements Serializable {INSTANCE; SafeSingleton () {//} public void singleton () {System. out. println ("hello !! ") ;}@ Testpublic void test16 () {// Collections2.filter (unfiltered, predicate); SafeSingleton. INSTANCE. singleton ();}

Each enum instance has a different subclass.


You can reload the method of an enum instance. This will efficiently give an enum instance an implementation of its own.

Package guava; public enum Operation {PLUS {double eval (double x, double y) {return x + y ;}, MINUS {double eval (double x, double y) {return x-y ;}, TIMES {double eval (double x, double y) {return x * y ;}}, DIVIDE {double eval (double x, double y) {return x/y ;}}; abstract double eval (double x, double y) ;}@ Testpublic void test () {double eval = Operation. DIVIDE. eval (12, 2); System. out. println (eval );}