JAVA design patterns-Singleton and singleton

JAVA design patterns-Singleton and singleton
Reprinted please indicate the source: http://blog.csdn.net/l1028386804/article/details/45441169
I,Overview

Ensure that a class has only one instance and provides a global access point to it.

II, Applicability

1. When the class can only have one instance and the customer can access it from a well-known access point.

2. When this unique instance should be extensible through subclass, and the customer should be able to use an extended instance without changing the code.

III, Participants

Singleton defines an Instance operation that allows the customer to access its unique Instance. An Instance is a class operation. It may be responsible for creating its own unique instance.

Iv. Category chart

V. Example

 Singleton

Package com. lyz. design. singleton;/*** create a Singleton object class * @ author liuyazhuang **/public class Singleton {/*** declare a static Singleton class variable */private static singlesing ton; /*** privatize the constructor */private Singleton () {}/ *** create a Singleton object * @ return */public static Singleton getInstance () {if (sing = null) {synchronized (Singleton. class) {if (sing = null) {sing = new Singleton () ;}} return sing ;}}

 Test

Package com. lyz. design. singleton;/*** Test class * @ author liuyazhuang **/public class Test {public static void main (String [] args) {Singleton sing = Singleton. getInstance (); Singleton sing2 = Singleton. getInstance (); System. out. println (sing); System. out. println (sing2 );}}

Result

com.lyz.design.singleton.Singleton@11f46b16com.lyz.design.singleton.Singleton@11f46b16