On the Java design pattern--Singleton mode (Singleton)

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One Overview

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

Two Applicability

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

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

Three participants

Singleton defines a instance operation that allows a client to access its only instance. Instance is a class operation. may be responsible for creating its own unique instance.

Four, class diagram

V. Examples

Singleton

Package com.lyz.design.singleton;/** * Class for creating singleton objects * @author Liuyazhuang * */public class Singleton {    /**     * declares a static sin Gleton class Variable     */    private static Singleton sing;    /**     * Construction Method Privatization * *    Private Singleton () {}    /**     * Create Singleton     * @return *     /public    static Singleton getinstance () {        if (sing = = null) {            synchronized (singleton.class) {if (sing = = null) {sing = new single ton ();        }}} return sing;}    }

Test

Package com.lyz.design.singleton;/** * Testing class * @author Liuyazhuang * */public class Test {public        static void main (Strin G[] args) {        Singleton sing = Singleton.getinstance ();        Singleton sing2 = Singleton.getinstance ();                System.out.println (sing);        System.out.println (sing2);    }}

Result

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On the Java design pattern--Singleton mode (Singleton)