🔖 死锁示例

Author: dunwu

codes/concurrent/src/main/java/io/github/dunwu/javase/concurrent/lock/DeadLockDemo.java

@@ -0,0 +1,57 @@
+package io.github.dunwu.javase.concurrent.lock;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * 死锁示例
+ * @see DeadLockFixDemo
+ */
+@SuppressWarnings("all")
+public class DeadLockDemo {
+
+    public static void main(String[] args) throws InterruptedException {
+        List<Integer> list1 = new ArrayList<>(Arrays.asList(2, 4, 6, 8, 10));
+        List<Integer> list2 = new ArrayList<>(Arrays.asList(1, 3, 7, 9, 11));
+
+        Thread thread1 = new Thread(() -> {
+            moveListItem(list1, list2, 2);
+        });
+        Thread thread2 = new Thread(() -> {
+            moveListItem(list2, list1, 9);
+        });
+
+        thread1.start();
+        thread2.start();
+        thread1.join();
+        thread2.join();
+        System.out.println(list1);
+        System.out.println(list2);
+    }
+
+    private static void moveListItem(List<Integer> from, List<Integer> to, Integer item) {
+        log("attempting lock for list", from);
+        synchronized (from) {
+            log("lock acquired for list", from);
+            try {
+                TimeUnit.SECONDS.sleep(1);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            log("attempting lock for list ", to);
+            synchronized (to) {
+                log("lock acquired for list", to);
+                if (from.remove(item)) {
+                    to.add(item);
+                }
+                log("moved item to list ", to);
+            }
+        }
+    }
+
+    private static void log(String msg, Object target) {
+        System.out.println(Thread.currentThread().getName() + ": " + msg + " " + System.identityHashCode(target));
+    }
+}

codes/concurrent/src/main/java/io/github/dunwu/javase/concurrent/lock/DeadLockFixDemo.java

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+package io.github.dunwu.javase.concurrent.lock;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * 解决死锁示例
+ * @see DeadLockDemo
+ */
+@SuppressWarnings("all")
+public class DeadLockFixDemo {
+
+    public static void main(String[] args) throws InterruptedException {
+        List<Integer> list1 = new ArrayList<>(Arrays.asList(2, 4, 6, 8, 10));
+        List<Integer> list2 = new ArrayList<>(Arrays.asList(1, 3, 7, 9, 11));
+
+        Thread thread1 = new Thread(() -> {
+            moveListItem(list1, list2, 2);
+        });
+        Thread thread2 = new Thread(() -> {
+            moveListItem(list2, list1, 9);
+        });
+
+        thread1.start();
+        thread2.start();
+        thread1.join();
+        thread2.join();
+        System.out.println(list1);
+        System.out.println(list2);
+    }
+
+    private static void moveListItem(List<Integer> from, List<Integer> to, Integer item) {
+        log("attempting lock for list", from);
+        boolean removedSuccessful = false;
+
+        synchronized (from) {
+            log("lock acquired for list", from);
+            try {
+                TimeUnit.SECONDS.sleep(1);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            removedSuccessful = from.remove(item);
+        }
+        if (removedSuccessful) {
+            log("attempting lock for list ", to);
+            synchronized (to) {
+                log("lock acquired for list", to);
+
+                to.add(item);
+                log("moved item to list ", to);
+            }
+        }
+    }
+
+    private static void log(String msg, Object target) {
+        System.out.println(Thread.currentThread().getName() + ": " + msg + " " + System.identityHashCode(target));
+    }
+}