设计模式之Singleton和Strategy

bjmashibing · bjmashibing · commit e6c8ca740a0e · 2019-05-07T22:10:16.000+08:00
diff --git a/.idea/encodings.xml b/.idea/encodings.xml
diff --git a/.idea/workspace.xml b/.idea/workspace.xml
diff --git a/out/production/DesignPatterns/com/mashibing/dp/cor/FilterChain.class b/out/production/DesignPatterns/com/mashibing/dp/cor/FilterChain.class
diff --git a/src/com/mashibing/singleton/Main.java b/src/com/mashibing/singleton/Main.java
@@ -0,0 +1,8 @@
+package com.mashibing.singleton;
+
+public class Main {
+
+    public static void main(String[] args) {
+        //Mgr01 mgr = Mgr01.getInstance();
+    }
+}
diff --git a/src/com/mashibing/singleton/Mgr01.java b/src/com/mashibing/singleton/Mgr01.java
@@ -0,0 +1,29 @@
+package com.mashibing.singleton;
+
+/**
+ * 饿汉式
+ * 类加载到内存后，就实例化一个单例，JVM保证线程安全
+ * 简单实用，推荐使用！
+ * 唯一缺点：不管用到与否，类装载时就完成实例化
+ * Class.forName("")
+ * （话说你不用的，你装载它干啥）
+ */
+public class Mgr01 {
+    private static final Mgr01 INSTANCE = new Mgr01();
+
+    private Mgr01() {};
+
+    public static Mgr01 getInstance() {
+        return INSTANCE;
+    }
+
+    public void m() {
+        System.out.println("m");
+    }
+
+    public static void main(String[] args) {
+        Mgr01 m1 = Mgr01.getInstance();
+        Mgr01 m2 = Mgr01.getInstance();
+        System.out.println(m1 == m2);
+    }
+}
diff --git a/src/com/mashibing/singleton/Mgr02.java b/src/com/mashibing/singleton/Mgr02.java
@@ -0,0 +1,27 @@
+package com.mashibing.singleton;
+
+/**
+ * 跟01是一个意思
+ */
+public class Mgr02 {
+    private static final Mgr02 INSTANCE;
+    static {
+        INSTANCE = new Mgr02();
+    }
+
+    private Mgr02() {};
+
+    public static Mgr02 getInstance() {
+        return INSTANCE;
+    }
+
+    public void m() {
+        System.out.println("m");
+    }
+
+    public static void main(String[] args) {
+        Mgr02 m1 = Mgr02.getInstance();
+        Mgr02 m2 = Mgr02.getInstance();
+        System.out.println(m1 == m2);
+    }
+}
diff --git a/src/com/mashibing/singleton/Mgr03.java b/src/com/mashibing/singleton/Mgr03.java
@@ -0,0 +1,37 @@
+package com.mashibing.singleton;
+
+/**
+ * lazy loading
+ * 也称懒汉式
+ * 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
+ */
+public class Mgr03 {
+    private static Mgr03 INSTANCE;
+
+    private Mgr03() {
+    }
+
+    public static Mgr03 getInstance() {
+        if (INSTANCE == null) {
+            try {
+                Thread.sleep(1);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            INSTANCE = new Mgr03();
+        }
+        return INSTANCE;
+    }
+
+    public void m() {
+        System.out.println("m");
+    }
+
+    public static void main(String[] args) {
+        for(int i=0; i<100; i++) {
+            new Thread(()->
+                System.out.println(Mgr03.getInstance().hashCode())
+            ).start();
+        }
+    }
+}
diff --git a/src/com/mashibing/singleton/Mgr04.java b/src/com/mashibing/singleton/Mgr04.java
@@ -0,0 +1,38 @@
+package com.mashibing.singleton;
+
+/**
+ * lazy loading
+ * 也称懒汉式
+ * 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
+ * 可以通过synchronized解决，但也带来效率下降
+ */
+public class Mgr04 {
+    private static Mgr04 INSTANCE;
+
+    private Mgr04() {
+    }
+
+    public static synchronized Mgr04 getInstance() {
+        if (INSTANCE == null) {
+            try {
+                Thread.sleep(1);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            INSTANCE = new Mgr04();
+        }
+        return INSTANCE;
+    }
+
+    public void m() {
+        System.out.println("m");
+    }
+
+    public static void main(String[] args) {
+        for(int i=0; i<100; i++) {
+            new Thread(()->{
+                System.out.println(Mgr04.getInstance().hashCode());
+            }).start();
+        }
+    }
+}
diff --git a/src/com/mashibing/singleton/Mgr05.java b/src/com/mashibing/singleton/Mgr05.java
@@ -0,0 +1,41 @@
+package com.mashibing.singleton;
+
+/**
+ * lazy loading
+ * 也称懒汉式
+ * 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
+ * 可以通过synchronized解决，但也带来效率下降
+ */
+public class Mgr05 {
+    private static Mgr05 INSTANCE;
+
+    private Mgr05() {
+    }
+
+    public static Mgr05 getInstance() {
+        if (INSTANCE == null) {
+            //妄图通过减小同步代码块的方式提高效率，然后不可行
+            synchronized (Mgr05.class) {
+                try {
+                    Thread.sleep(1);
+                } catch (InterruptedException e) {
+                    e.printStackTrace();
+                }
+                INSTANCE = new Mgr05();
+            }
+        }
+        return INSTANCE;
+    }
+
+    public void m() {
+        System.out.println("m");
+    }
+
+    public static void main(String[] args) {
+        for(int i=0; i<100; i++) {
+            new Thread(()->{
+                System.out.println(Mgr05.getInstance().hashCode());
+            }).start();
+        }
+    }
+}
diff --git a/src/com/mashibing/singleton/Mgr06.java b/src/com/mashibing/singleton/Mgr06.java
@@ -0,0 +1,43 @@
+package com.mashibing.singleton;
+
+/**
+ * lazy loading
+ * 也称懒汉式
+ * 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
+ * 可以通过synchronized解决，但也带来效率下降
+ */
+public class Mgr06 {
+    private static volatile Mgr06 INSTANCE; //JIT
+
+    private Mgr06() {
+    }
+
+    public static Mgr06 getInstance() {
+        if (INSTANCE == null) {
+            //双重检查
+            synchronized (Mgr06.class) {
+                if(INSTANCE == null) {
+                    try {
+                        Thread.sleep(1);
+                    } catch (InterruptedException e) {
+                        e.printStackTrace();
+                    }
+                    INSTANCE = new Mgr06();
+                }
+            }
+        }
+        return INSTANCE;
+    }
+
+    public void m() {
+        System.out.println("m");
+    }
+
+    public static void main(String[] args) {
+        for(int i=0; i<100; i++) {
+            new Thread(()->{
+                System.out.println(Mgr06.getInstance().hashCode());
+            }).start();
+        }
+    }
+}
diff --git a/src/com/mashibing/singleton/Mgr07.java b/src/com/mashibing/singleton/Mgr07.java
@@ -0,0 +1,34 @@
+package com.mashibing.singleton;
+
+/**
+ * 静态内部类方式
+ * JVM保证单例
+ * 加载外部类时不会加载内部类，这样可以实现懒加载
+ */
+public class Mgr07 {
+
+    private Mgr07() {
+    }
+
+    private static class Mgr07Holder {
+        private final static Mgr07 INSTANCE = new Mgr07();
+    }
+
+    public static Mgr07 getInstance() {
+        return Mgr07Holder.INSTANCE;
+    }
+
+    public void m() {
+        System.out.println("m");
+    }
+
+    public static void main(String[] args) {
+        for(int i=0; i<100; i++) {
+            new Thread(()->{
+                System.out.println(Mgr07.getInstance().hashCode());
+            }).start();
+        }
+    }
+
+
+}
diff --git a/src/com/mashibing/singleton/Mgr08.java b/src/com/mashibing/singleton/Mgr08.java
@@ -0,0 +1,20 @@
+package com.mashibing.singleton;
+
+/**
+ * 不仅可以解决线程同步，还可以防止反序列化。
+ */
+public enum Mgr08 {
+
+    INSTANCE;
+
+    public void m() {}
+
+    public static void main(String[] args) {
+        for(int i=0; i<100; i++) {
+            new Thread(()->{
+                System.out.println(Mgr08.INSTANCE.hashCode());
+            }).start();
+        }
+    }
+
+}
diff --git a/src/com/mashibing/strategy/Cat.java b/src/com/mashibing/strategy/Cat.java
@@ -0,0 +1,25 @@
+package com.mashibing.strategy;
+
+public class Cat implements Comparable<Cat> {
+    int weight, height;
+
+    public Cat(int weight, int height) {
+        this.weight = weight;
+        this.height = height;
+    }
+
+    public int compareTo(Cat c) {
+
+        if(this.weight < c.weight) return -1;
+        else if(this.weight > c.weight) return 1;
+        else return 0;
+    }
+
+    @Override
+    public String toString() {
+        return "Cat{" +
+                "weight=" + weight +
+                ", height=" + height +
+                '}';
+    }
+}
diff --git a/src/com/mashibing/strategy/CatHeightComparator.java b/src/com/mashibing/strategy/CatHeightComparator.java
@@ -0,0 +1,10 @@
+package com.mashibing.strategy;
+
+public class CatHeightComparator implements Comparator<Cat> {
+    @Override
+    public int compare(Cat o1, Cat o2) {
+        if(o1.height > o2.height) return -1;
+        else if (o1.height < o2.height) return 1;
+        else return 0;
+    }
+}
diff --git a/src/com/mashibing/strategy/CatWeightComparator.java b/src/com/mashibing/strategy/CatWeightComparator.java
@@ -0,0 +1,10 @@
+package com.mashibing.strategy;
+
+public class CatWeightComparator implements Comparator<Cat> {
+    @Override
+    public int compare(Cat o1, Cat o2) {
+        if(o1.weight < o2.weight) return -1;
+        else if (o1.weight > o2.weight) return 1;
+        else return 0;
+    }
+}
diff --git a/src/com/mashibing/strategy/Comparable.java b/src/com/mashibing/strategy/Comparable.java
@@ -0,0 +1,5 @@
+package com.mashibing.strategy;
+
+public interface Comparable<T> {
+    int compareTo(T o);
+}
diff --git a/src/com/mashibing/strategy/Comparator.java b/src/com/mashibing/strategy/Comparator.java
@@ -0,0 +1,5 @@
+package com.mashibing.strategy;
+
+public interface Comparator<T> {
+    int compare(T o1, T o2);
+}
diff --git a/src/com/mashibing/strategy/Dog.java b/src/com/mashibing/strategy/Dog.java
@@ -0,0 +1,24 @@
+package com.mashibing.strategy;
+
+public class Dog implements Comparable<Dog> {
+
+    int food;
+
+    public Dog(int food) {
+        this.food = food;
+    }
+
+    @Override
+    public int compareTo(Dog d) {
+        if(this.food < d.food) return -1;
+        else if(this.food > d.food) return 1;
+        else return 0;
+    }
+
+    @Override
+    public String toString() {
+        return "Dog{" +
+                "food=" + food +
+                '}';
+    }
+}
diff --git a/src/com/mashibing/strategy/DogComparator.java b/src/com/mashibing/strategy/DogComparator.java
@@ -0,0 +1,10 @@
+package com.mashibing.strategy;
+
+public class DogComparator implements Comparator<Dog> {
+    @Override
+    public int compare(Dog o1, Dog o2) {
+        if(o1.food < o2.food) return -1;
+        else if (o1.food > o2.food) return 1;
+        else return 0;
+    }
+}
diff --git a/src/com/mashibing/strategy/Main.java b/src/com/mashibing/strategy/Main.java
diff --git a/src/com/mashibing/strategy/Sorter.java b/src/com/mashibing/strategy/Sorter.java
