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设计模式之Singleton和Strategy
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Lines changed: 794 additions & 70 deletions

‎.idea/encodings.xml‎

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‎.idea/workspace.xml‎

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‎out/production/DesignPatterns/com/mashibing/dp/cor/FilterChain.class‎

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‎src/com/mashibing/singleton/Main.java‎

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package com.mashibing.singleton;
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public class Main {
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public static void main(String[] args) {
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//Mgr01 mgr = Mgr01.getInstance();
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}
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}

‎src/com/mashibing/singleton/Mgr01.java‎

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package com.mashibing.singleton;
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/**
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* 饿汉式
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* 类加载到内存后，就实例化一个单例，JVM保证线程安全
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* 简单实用，推荐使用！
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* 唯一缺点：不管用到与否，类装载时就完成实例化
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* Class.forName("")
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* （话说你不用的，你装载它干啥）
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*/
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public class Mgr01 {
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private static final Mgr01 INSTANCE = new Mgr01();
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private Mgr01() {};
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public static Mgr01 getInstance() {
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return INSTANCE;
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}
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public void m() {
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System.out.println("m");
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}
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public static void main(String[] args) {
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Mgr01 m1 = Mgr01.getInstance();
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Mgr01 m2 = Mgr01.getInstance();
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System.out.println(m1 == m2);
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}
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}

‎src/com/mashibing/singleton/Mgr02.java‎

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package com.mashibing.singleton;
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/**
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* 跟01是一个意思
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*/
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public class Mgr02 {
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private static final Mgr02 INSTANCE;
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static {
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INSTANCE = new Mgr02();
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}
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private Mgr02() {};
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public static Mgr02 getInstance() {
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return INSTANCE;
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}
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public void m() {
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System.out.println("m");
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}
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public static void main(String[] args) {
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Mgr02 m1 = Mgr02.getInstance();
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Mgr02 m2 = Mgr02.getInstance();
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System.out.println(m1 == m2);
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}
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}

‎src/com/mashibing/singleton/Mgr03.java‎

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package com.mashibing.singleton;
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/**
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* lazy loading
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* 也称懒汉式
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* 虽然达到了按需初始化的目的，但却带来线程不安全的问题
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*/
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public class Mgr03 {
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private static Mgr03 INSTANCE;
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private Mgr03() {
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}
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public static Mgr03 getInstance() {
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if (INSTANCE == null) {
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try {
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Thread.sleep(1);
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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INSTANCE = new Mgr03();
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}
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return INSTANCE;
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}
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public void m() {
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System.out.println("m");
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}
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public static void main(String[] args) {
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for(int i=0; i<100; i++) {
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new Thread(()->
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System.out.println(Mgr03.getInstance().hashCode())
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).start();
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}
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}
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}

‎src/com/mashibing/singleton/Mgr04.java‎

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package com.mashibing.singleton;
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/**
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* lazy loading
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* 也称懒汉式
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* 虽然达到了按需初始化的目的，但却带来线程不安全的问题
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* 可以通过synchronized解决，但也带来效率下降
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*/
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public class Mgr04 {
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private static Mgr04 INSTANCE;
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private Mgr04() {
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}
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public static synchronized Mgr04 getInstance() {
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if (INSTANCE == null) {
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try {
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Thread.sleep(1);
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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INSTANCE = new Mgr04();
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}
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return INSTANCE;
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}
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public void m() {
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System.out.println("m");
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}
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public static void main(String[] args) {
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for(int i=0; i<100; i++) {
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new Thread(()->{
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System.out.println(Mgr04.getInstance().hashCode());
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}).start();
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}
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}
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}

‎src/com/mashibing/singleton/Mgr05.java‎

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package com.mashibing.singleton;
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/**
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* lazy loading
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* 也称懒汉式
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* 虽然达到了按需初始化的目的，但却带来线程不安全的问题
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* 可以通过synchronized解决，但也带来效率下降
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*/
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public class Mgr05 {
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private static Mgr05 INSTANCE;
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private Mgr05() {
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}
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public static Mgr05 getInstance() {
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if (INSTANCE == null) {
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//妄图通过减小同步代码块的方式提高效率，然后不可行
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synchronized (Mgr05.class) {
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try {
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Thread.sleep(1);
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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INSTANCE = new Mgr05();
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}
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}
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return INSTANCE;
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}
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public void m() {
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System.out.println("m");
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}
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public static void main(String[] args) {
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for(int i=0; i<100; i++) {
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new Thread(()->{
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System.out.println(Mgr05.getInstance().hashCode());
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}).start();
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}
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}
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}

‎src/com/mashibing/singleton/Mgr06.java‎

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package com.mashibing.singleton;
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/**
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* lazy loading
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* 也称懒汉式
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* 虽然达到了按需初始化的目的，但却带来线程不安全的问题
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* 可以通过synchronized解决，但也带来效率下降
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*/
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public class Mgr06 {
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private static volatile Mgr06 INSTANCE; //JIT
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private Mgr06() {
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}
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public static Mgr06 getInstance() {
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if (INSTANCE == null) {
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//双重检查
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synchronized (Mgr06.class) {
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if(INSTANCE == null) {
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try {
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Thread.sleep(1);
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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INSTANCE = new Mgr06();
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}
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}
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}
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return INSTANCE;
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}
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public void m() {
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System.out.println("m");
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}
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public static void main(String[] args) {
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for(int i=0; i<100; i++) {
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new Thread(()->{
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System.out.println(Mgr06.getInstance().hashCode());
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}).start();
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}
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}
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}

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