/*

 Some class,such as a config file,need to be only one.So we need to control the instance.

 1,private the constructor and create only one instance in the class itself.

 2,provide a method for the others to get the 'only one' instance.

 */

 package kju.obj;

 import static kju.print.Printer.*;

 public class SingletonDemo {

     public static void main(String[] args) {

         SingleConfig con01 = SingleConfig.getInstance();

         SingleConfig con02 = SingleConfig.getInstance();

         println("con01 color : " + con01.getColor());

         println("con02 set color : ");

         con02.setColor("Blue");

         println("con01 color : " + con01.getColor());

         /*

         con01 color : Orange

         con02 set color :

         con01 color : Blue

         */

     }

 }

 class SingleConfig {

     private String color = "Orange";

     private static SingleConfig s = new SingleConfig();

     private SingleConfig() {}

     public static SingleConfig getInstance() {

         return s;

     }

     public void setColor(String color) {

         this.color = color;

     }

     public String getColor() {

         return color;

     }

 }