BAEL-3837: Java Deadlock and Livelock (#8943)

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/deadlockAndLivelock/DeadlockExample.java

@@ -0,0 +1,60 @@
+package com.baeldung.deadlockAndLivelock;
+
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+public class DeadlockExample {
+
+    private Lock lock1 = new ReentrantLock(true);
+    private Lock lock2 = new ReentrantLock(true);
+
+    public static void main(String[] args) {
+        DeadlockExample deadlock = new DeadlockExample();
+        new Thread(deadlock::operation1, "T1").start();
+        new Thread(deadlock::operation2, "T2").start();
+
+    }
+
+    public void operation1() {
+        lock1.lock();
+        print("lock1 acquired, waiting to acquire lock2.");
+        sleep(50);
+
+        lock2.lock();
+        print("lock2 acquired");
+
+        print("executing first operation.");
+
+        lock2.unlock();
+        lock1.unlock();
+
+    }
+
+    public void operation2() {
+        lock2.lock();
+        print("lock2 acquired, waiting to acquire lock1.");
+        sleep(50);
+
+        lock1.lock();
+        print("lock1 acquired");
+
+        print("executing second operation.");
+
+        lock1.unlock();
+        lock2.unlock();
+    }
+
+    public void print(String message) {
+        System.out.println("Thread " + Thread.currentThread()
+            .getName() + ": " + message);
+    }
+
+    public void sleep(long millis) {
+        try {
+            Thread.sleep(millis);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
+
+}

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/deadlockAndLivelock/LivelockExample.java

@@ -0,0 +1,86 @@
+package com.baeldung.deadlockAndLivelock;
+
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+public class LivelockExample {
+
+    private Lock lock1 = new ReentrantLock(true);
+    private Lock lock2 = new ReentrantLock(true);
+
+    public static void main(String[] args) {
+        LivelockExample livelock = new LivelockExample();
+        new Thread(livelock::operation1, "T1").start();
+        new Thread(livelock::operation2, "T2").start();
+
+    }
+
+    public void operation1() {
+        while (true) {
+            tryLock(lock1, 50);
+            print("lock1 acquired, trying to acquire lock2.");
+            sleep(50);
+
+            if (tryLock(lock2)) {
+                print("lock2 acquired.");
+            } else {
+                print("cannot acquire lock2, releasing lock1.");
+                lock1.unlock();
+                continue;
+            }
+
+            print("executing first operation.");
+            break;
+        }
+        lock2.unlock();
+        lock1.unlock();
+    }
+
+    public void operation2() {
+        while (true) {
+            tryLock(lock2, 50);
+            print("lock2 acquired, trying to acquire lock1.");
+            sleep(50);
+
+            if (tryLock(lock1)) {
+                print("lock1 acquired.");
+            } else {
+                print("cannot acquire lock1, releasing lock2.");
+                lock2.unlock();
+                continue;
+            }
+
+            print("executing second operation.");
+            break;
+        }
+        lock1.unlock();
+        lock2.unlock();
+    }
+
+    public void print(String message) {
+        System.out.println("Thread " + Thread.currentThread()
+            .getName() + ": " + message);
+    }
+
+    public void sleep(long millis) {
+        try {
+            Thread.sleep(millis);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public void tryLock(Lock lock, long millis) {
+        try {
+            lock.tryLock(10, TimeUnit.MILLISECONDS);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public boolean tryLock(Lock lock) {
+        return lock.tryLock();
+    }
+
+}