Thread Security

Author: CodePrometheus

README.md

@@ -10,9 +10,10 @@ Java并发编程
      Thread和Object中的重要方法
      线程的属性
      未捕获异常的处理
+     线程安全问题
      ThreadPool
      ThreadLocal
-
+     
 
 ## 锁
      乐观与悲观锁

Thread/src/threadsecurity/DeadLock.java

@@ -0,0 +1,54 @@
+package threadsecurity;
+
+/**
+ * 演示死锁 发布逸出
+ *
+ * @Author: zzStar
+ * @Date: 10-19-2020 11:46
+ */
+public class DeadLock implements Runnable {
+
+    int flag = 1;
+    static Object object1 = new Object();
+    static Object object2 = new Object();
+
+    public static void main(String[] args) {
+        DeadLock deadLock1 = new DeadLock();
+        DeadLock deadLock2 = new DeadLock();
+        deadLock1.flag = 1;
+        deadLock2.flag = 0;
+        new Thread(deadLock1).start();
+        new Thread(deadLock2).start();
+    }
+
+    @Override
+    public void run() {
+        System.out.println("flag = " + flag);
+        if (flag == 1) {
+            synchronized (object1) {
+                try {
+                    Thread.sleep(500);
+                } catch (InterruptedException e) {
+                    e.printStackTrace();
+                }
+                synchronized (object2) {
+                    System.out.println("1");
+                }
+            }
+        }
+
+        if (flag == 0) {
+            synchronized (object2) {
+                try {
+                    Thread.sleep(500);
+                } catch (InterruptedException e) {
+                    e.printStackTrace();
+                }
+                synchronized (object1) {
+                    System.out.println("1");
+                }
+            }
+        }
+
+    }
+}

Thread/src/threadsecurity/FactoryPattern.java

@@ -0,0 +1,76 @@
+package threadsecurity;
+
+/**
+ * 工厂模式修复初始化问题
+ *
+ * @Author: zzStar
+ * @Date: 10-19-2020 13:01
+ */
+public class FactoryPattern {
+
+    int count;
+    private EventListener listener;
+
+    // 保护起来
+    private FactoryPattern(MySource mySource) {
+
+        listener = e -> System.out.println("得到的数字是" + count);
+
+        for (int i = 0; i < 1000; i++) {
+            System.out.print(i);
+        }
+        count = 100;
+    }
+
+    // 工厂方法
+    public static FactoryPattern getInstance(MySource mySource) {
+        FactoryPattern factoryPattern = new FactoryPattern(mySource);
+        // 完成所有准备工作再注册
+        mySource.registerListener(factoryPattern.listener);
+        return factoryPattern;
+    }
+
+    public static void main(String[] args) {
+        MySource mySource = new MySource();
+
+        new Thread(() -> {
+            try {
+                Thread.sleep(10);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            mySource.eventCome(new Event() {
+            });
+        }).start();
+
+        // 初始化
+        FactoryPattern factoryPattern = new FactoryPattern(mySource);
+    }
+
+    static class MySource {
+
+        // 注册监听器
+        private EventListener listener;
+
+        void registerListener(EventListener eventListener) {
+            this.listener = eventListener;
+        }
+
+        void eventCome(Event e) {
+            if (listener != null) {
+                listener.onEvent(e);
+            } else {
+                System.out.println("还未初始化完毕");
+            }
+        }
+    }
+
+    interface EventListener {
+        void onEvent(Event e);
+    }
+
+    interface Event {
+
+    }
+
+}

Thread/src/threadsecurity/MultiThreadError.java

@@ -0,0 +1,92 @@
+package threadsecurity;
+
+import java.util.concurrent.BrokenBarrierException;
+import java.util.concurrent.CyclicBarrier;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * 1.运行结果出错
+ * 计数不准确，并且找出具体出错的位置
+ *
+ * @Author: zzStar
+ * @Date: 10-18-2020 19:38
+ */
+public class MultiThreadError implements Runnable {
+
+    int index = 0;
+
+    static AtomicInteger realIndex = new AtomicInteger();
+    static AtomicInteger wrongCount = new AtomicInteger();
+
+    // 等待共同出发
+    static volatile CyclicBarrier cyclicBarrier1 = new CyclicBarrier(2);
+    static volatile CyclicBarrier cyclicBarrier2 = new CyclicBarrier(2);
+
+    final boolean[] marked = new boolean[30000];
+
+    static MultiThreadError multiThreadError = new MultiThreadError();
+
+    public static void main(String[] args) throws InterruptedException {
+        Thread thread1 = new Thread(multiThreadError);
+        Thread thread2 = new Thread(multiThreadError);
+        thread1.start();
+        thread2.start();
+        // 使得主线程等待两个子线程停止
+        thread1.join();
+        thread2.join();
+        System.out.println("表面上运行的结果" + multiThreadError.index);//<20000
+        System.out.println("真正运行的次数" + realIndex.get());
+        System.out.println("错误运行的次数" + wrongCount.get());
+    }
+
+
+    @Override
+    public void run() {
+/*
+        while (index < 1000) {
+            index++;
+        }
+*/
+        marked[0] = true;
+
+        for (int i = 0; i < 10000; i++) {
+
+            // 两个线程都到await才继续
+            try {
+                cyclicBarrier2.reset();
+                cyclicBarrier1.await();
+            } catch (InterruptedException | BrokenBarrierException e) {
+                e.printStackTrace();
+            }
+
+            index++;
+
+            // 都++后就才继续
+            try {
+                cyclicBarrier1.reset();
+                cyclicBarrier2.await();
+            } catch (InterruptedException | BrokenBarrierException e) {
+                e.printStackTrace();
+            }
+
+            // 原子操作下准确的值
+            realIndex.incrementAndGet();
+
+            // 这里需要同步，确保不被打断，并且保证可见性
+            synchronized (multiThreadError) {
+
+                // 前一位也必须是true
+                if (marked[index] && marked[index - 1]) {
+                    System.out.println("发生错误已被标记" + index);
+                    // 发生的错误数也增加
+                    wrongCount.incrementAndGet();
+                }
+
+                // 存进marked，标记
+                marked[index] = true;
+            }
+        }
+    }
+
+
+}

Thread/src/threadsecurity/NewThreadConstructor.java

@@ -0,0 +1,40 @@
+package threadsecurity;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * 构造函数中新建线程
+ *
+ * @Author: zzStar
+ * @Date: 10-19-2020 12:48
+ */
+public class NewThreadConstructor {
+
+    private Map<String, String> states;
+
+
+    // 构造函数中新建线程
+    public NewThreadConstructor() {
+        new Thread(() -> {
+            states = new HashMap<>();
+            states.put("1", "a");
+            states.put("2", "b");
+            states.put("3", "c");
+        }).start();
+    }
+
+    public Map<String, String> getStates() {
+        return states;
+    }
+
+    public static void main(String[] args) throws InterruptedException {
+        NewThreadConstructor newThreadConstructor = new NewThreadConstructor();
+        // java.lang.NullPointerException
+        // 初始化的工作在另外一个线程还没执行完毕
+        // 时间不同，结果不同
+        Thread.sleep(1000);
+        System.out.println(newThreadConstructor.getStates().get("1"));
+
+    }
+}

Thread/src/threadsecurity/Observer.java

@@ -0,0 +1,70 @@
+package threadsecurity;
+
+/**
+ * 观察者模式
+ * 利用工厂模式解决问题
+ *
+ * @Author: zzStar
+ * @Date: 10-19-2020 12:23
+ */
+public class Observer {
+
+    int count;
+
+    public Observer(MySource mySource) {
+
+        // 匿名内部类中持有外部类的引用
+        mySource.registerListener((Event e) -> {
+            // 我得到的数字是0
+            System.out.println("\n我得到的数字是" + count);
+        });
+
+        for (int i = 0; i < 1000; i++) {
+            System.out.print(i);
+        }
+        count = 100;
+    }
+
+    public static void main(String[] args) {
+        MySource mySource = new MySource();
+
+        new Thread(() -> {
+            try {
+                Thread.sleep(10);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            mySource.eventCome(new Event() {
+            });
+        }).start();
+
+        // 初始化
+        Observer observer = new Observer(mySource);
+    }
+
+    static class MySource {
+
+        // 注册监听器
+        private EventListener listener;
+
+        void registerListener(EventListener eventListener) {
+            this.listener = eventListener;
+        }
+
+        void eventCome(Event e) {
+            if (listener != null) {
+                listener.onEvent(e);
+            } else {
+                System.out.println("还未初始化完毕");
+            }
+        }
+    }
+
+    interface EventListener {
+        void onEvent(Event e);
+    }
+
+    interface Event {
+
+    }
+}

Thread/src/threadsecurity/Problem.png

@@ -0,0 +1,49 @@
+package threadsecurity;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * 发布逸出
+ * 利用副本解决问题
+ *
+ * @Author: zzStar
+ * @Date: 10-19-2020 11:55
+ */
+public class ReleaseEscape {
+
+    // 这里定义为private
+    private Map<String, String> states;
+
+    public ReleaseEscape() {
+        states = new HashMap<>();
+        states.put("1", "a");
+        states.put("2", "b");
+        states.put("3", "c");
+    }
+
+    public Map<String, String> getStates() {
+        // 这里把private发布了
+        return states;
+    }
+
+    public Map<String, String> getStatesImproved() {
+        return new HashMap<>(states);
+    }
+
+    public static void main(String[] args) {
+        ReleaseEscape releaseEscape = new ReleaseEscape();
+        Map<String, String> states = releaseEscape.getStates();
+/*
+        System.out.println(states.get("1"));
+        // 被篡改
+        states.remove("1");
+        // null
+        System.out.println(states.get("1"));
+*/
+        System.out.println(releaseEscape.getStatesImproved().get("1"));
+        releaseEscape.getStatesImproved().remove("1");
+        // Copied
+        System.out.println(releaseEscape.getStatesImproved().get("1"));
+    }
+}