BAEL-700 Guide to Java Lock API (#1239)

* BAEL-604 Introduction to apache velocity

* BAEL-604 Introduction to apache velocity

* BAEL-700 Guide to Java Lock APIs

* BAEL-700 Guide to Java Lock APIs

core-java/src/test/java/com/baeldung/concurrent/locks/SharedObjectWithLockManualTest.java

@@ -0,0 +1,75 @@
+package com.baeldung.concurrent.locks;
+
+import org.junit.Test;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import static junit.framework.TestCase.assertEquals;
+
+public class SharedObjectWithLockManualTest {
+
+	@Test
+	public void whenLockAcquired_ThenLockedIsTrue() {
+		final SharedObjectWithLock object = new SharedObjectWithLock();
+
+		final int threadCount = 2;
+		final ExecutorService service = Executors.newFixedThreadPool(threadCount);
+
+		executeThreads(object, threadCount, service);
+
+		assertEquals(true, object.isLocked());
+
+		service.shutdown();
+	}
+
+	@Test
+	public void whenLocked_ThenQueuedThread() {
+		final int threadCount = 4;
+		final ExecutorService service = Executors.newFixedThreadPool(threadCount);
+		final SharedObjectWithLock object = new SharedObjectWithLock();
+
+		executeThreads(object, threadCount, service);
+
+		assertEquals(object.hasQueuedThreads(), true);
+
+		service.shutdown();
+
+	}
+
+	public void whenTryLock_ThenQueuedThread() {
+		final SharedObjectWithLock object = new SharedObjectWithLock();
+
+		final int threadCount = 2;
+		final ExecutorService service = Executors.newFixedThreadPool(threadCount);
+
+		executeThreads(object, threadCount, service);
+
+		assertEquals(true, object.isLocked());
+
+		service.shutdown();
+	}
+
+	@Test
+	public void whenGetCount_ThenCorrectCount() throws InterruptedException {
+		final int threadCount = 4;
+		final ExecutorService service = Executors.newFixedThreadPool(threadCount);
+		final SharedObjectWithLock object = new SharedObjectWithLock();
+
+		executeThreads(object, threadCount, service);
+		Thread.sleep(1000);
+		assertEquals(object.getCounter(), 4);
+
+		service.shutdown();
+
+	}
+
+	private void executeThreads(SharedObjectWithLock object, int threadCount, ExecutorService service) {
+		for (int i = 0; i < threadCount; i++) {
+			service.execute(() -> {
+				object.perform();
+			});
+		}
+	}
+
+}

core-java/src/test/java/com/baeldung/concurrent/locks/SynchronizedHashMapWithRWLockManualTest.java

@@ -0,0 +1,58 @@
+package com.baeldung.concurrent.locks;
+
+import jdk.nashorn.internal.ir.annotations.Ignore;
+import org.junit.Test;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import static junit.framework.TestCase.assertEquals;
+
+public class SynchronizedHashMapWithRWLockManualTest {
+
+	@Test
+	public void whenWriting_ThenNoReading() {
+		SynchronizedHashMapWithRWLock object = new SynchronizedHashMapWithRWLock();
+		final int threadCount = 3;
+		final ExecutorService service = Executors.newFixedThreadPool(threadCount);
+
+		executeWriterThreads(object, threadCount, service);
+
+		assertEquals(object.isReadLockAvailable(), false);
+
+		service.shutdown();
+	}
+
+	@Test
+	public void whenReading_ThenMultipleReadingAllowed() {
+		SynchronizedHashMapWithRWLock object = new SynchronizedHashMapWithRWLock();
+		final int threadCount = 5;
+		final ExecutorService service = Executors.newFixedThreadPool(threadCount);
+
+		executeReaderThreads(object, threadCount, service);
+
+		assertEquals(object.isReadLockAvailable(), true);
+
+		service.shutdown();
+	}
+
+	private void executeWriterThreads(SynchronizedHashMapWithRWLock object, int threadCount, ExecutorService service) {
+		for (int i = 0; i < threadCount; i++) {
+			service.execute(() -> {
+				try {
+					object.put("key" + threadCount, "value" + threadCount);
+				} catch (InterruptedException e) {
+					e.printStackTrace();
+				}
+			});
+		}
+	}
+
+	private void executeReaderThreads(SynchronizedHashMapWithRWLock object, int threadCount, ExecutorService service) {
+		for (int i = 0; i < threadCount; i++)
+			service.execute(() -> {
+				object.get("key" + threadCount);
+			});
+	}
+
+}