merge from upstream

core-java-concurrency/src/main/java/com/baeldung/concurrent/daemon/NewThread.java

@@ -3,8 +3,18 @@
 public class NewThread extends Thread {
 
     public void run() {
-        while (true)
-            for (int i = 0; i < 10; i++)
-                System.out.println("New Thread is running...");
+
+    	long startTime = System.currentTimeMillis();
+        while (true) {
+            for (int i = 0; i < 10; i++) {
+                System.out.println("New Thread is running..." + i);
+            }
+
+            // prevent the Thread to run forever. It will finish it's execution after 2 seconds
+            if (System.currentTimeMillis() - startTime > 2000) {
+            	Thread.currentThread().interrupt();
+            	break;
+            }
+        }
     }
 }

core-java-concurrency/src/main/java/com/baeldung/concurrent/executorservice/DelayedCallable.java

@@ -0,0 +1,26 @@
+package com.baeldung.concurrent.executorservice;
+
+import java.util.concurrent.Callable;
+
+public class DelayedCallable implements Callable<String> {
+
+    private String name;
+    private long period;
+
+    public DelayedCallable(String name, long period) {
+        this.name = name;
+        this.period = period;
+    }
+
+    public String call() {
+
+        try {
+            Thread.sleep(period);
+        } catch (InterruptedException ex) {
+            // handle exception
+            ex.printStackTrace();
+        }
+
+        return name;
+    }
+}

core-java-concurrency/src/test/java/com/baeldung/concurrent/daemon/DaemonThreadTest.java

@@ -3,11 +3,13 @@
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
+import org.junit.Ignore;
 import org.junit.Test;
 
 public class DaemonThreadTest {
 
     @Test
+    @Ignore
     public void whenCallIsDaemon_thenCorrect() {
         NewThread daemonThread = new NewThread();
         NewThread userThread = new NewThread();
@@ -20,6 +22,7 @@ public void whenCallIsDaemon_thenCorrect() {
     }
 
     @Test(expected = IllegalThreadStateException.class)
+    @Ignore
     public void givenUserThread_whenSetDaemonWhileRunning_thenIllegalThreadStateException() {
         NewThread daemonThread = new NewThread();
         daemonThread.start();

core-java-concurrency/src/test/java/com/baeldung/concurrent/executorservice/WaitingForThreadsToFinishTest.java

@@ -0,0 +1,147 @@
+package com.baeldung.concurrent.executorservice;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.*;
+
+import static junit.framework.TestCase.assertTrue;
+
+public class WaitingForThreadsToFinishTest {
+
+    private static final Logger LOG = LoggerFactory.getLogger(WaitingForThreadsToFinishTest.class);
+    private final static ExecutorService WORKER_THREAD_POOL = Executors.newFixedThreadPool(10);
+
+    @Test
+    public void givenMultipleThreads_whenInvokeAll_thenMainThreadShouldWaitForAllToFinish() {
+
+        ExecutorService WORKER_THREAD_POOL = Executors.newFixedThreadPool(10);
+
+        List<Callable<String>> callables = Arrays.asList(new DelayedCallable("fast thread", 100), new DelayedCallable("slow thread", 3000));
+
+        try {
+            long startProcessingTime = System.currentTimeMillis();
+            List<Future<String>> futures = WORKER_THREAD_POOL.invokeAll(callables);
+
+            long totalProcessingTime = System.currentTimeMillis() - startProcessingTime;
+            assertTrue(totalProcessingTime >= 3000);
+
+            String firstThreadResponse = futures.get(0)
+                .get();
+            assertTrue("First response should be from the fast thread", "fast thread".equals(firstThreadResponse));
+
+            String secondThreadResponse = futures.get(1)
+                .get();
+            assertTrue("Last response should be from the slow thread", "slow thread".equals(secondThreadResponse));
+
+        } catch (ExecutionException | InterruptedException ex) {
+            ex.printStackTrace();
+        }
+
+        WORKER_THREAD_POOL.shutdown();
+    }
+
+    @Test
+    public void givenMultipleThreads_whenUsingCompletionService_thenMainThreadShouldWaitForAllToFinish() {
+
+        CompletionService<String> service = new ExecutorCompletionService<>(WORKER_THREAD_POOL);
+
+        List<Callable<String>> callables = Arrays.asList(new DelayedCallable("fast thread", 100), new DelayedCallable("slow thread", 3000));
+
+        for (Callable<String> callable : callables) {
+            service.submit(callable);
+        }
+
+        WORKER_THREAD_POOL.shutdown();
+
+        try {
+
+            long startProcessingTime = System.currentTimeMillis();
+
+            Future<String> future = service.take();
+            String firstThreadResponse = future.get();
+            long totalProcessingTime = System.currentTimeMillis() - startProcessingTime;
+
+            assertTrue("First response should be from the fast thread", "fast thread".equals(firstThreadResponse));
+            assertTrue(totalProcessingTime >= 100 && totalProcessingTime < 1000);
+            LOG.debug("Thread finished after: " + totalProcessingTime + " milliseconds");
+
+            future = service.take();
+            String secondThreadResponse = future.get();
+            totalProcessingTime = System.currentTimeMillis() - startProcessingTime;
+
+            assertTrue("Last response should be from the slow thread", "slow thread".equals(secondThreadResponse));
+            assertTrue(totalProcessingTime >= 3000 && totalProcessingTime < 4000);
+            LOG.debug("Thread finished after: " + totalProcessingTime + " milliseconds");
+
+        } catch (ExecutionException | InterruptedException ex) {
+            ex.printStackTrace();
+        }
+
+    }
+
+    @Test
+    public void givenMultipleThreads_whenUsingCompletableFutures_thenMainThreadShouldWaitForAllToFinish() {
+
+        CompletableFuture<String> future1 = CompletableFuture.supplyAsync(() -> {
+
+            try {
+                Thread.sleep(1000);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+
+            return "Hello";
+        });
+
+        CompletableFuture<String> future2 = CompletableFuture.supplyAsync(() -> {
+
+            try {
+                Thread.sleep(5000);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+
+            return "Beautiful";
+        });
+
+        CompletableFuture<String> future3 = CompletableFuture.supplyAsync(() -> {
+
+            try {
+                Thread.sleep(3000);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+
+            return "World";
+        });
+
+        long startProcessingTime = System.currentTimeMillis();
+        CompletableFuture<Void> combinedFuture = CompletableFuture.allOf(future1, future2, future3);
+        combinedFuture.join();
+
+        long totalProcessingTime = System.currentTimeMillis() - startProcessingTime;
+        assertTrue(totalProcessingTime >= 5000 && totalProcessingTime < 6000);
+
+        LOG.debug("Responses from all threads are available after " + totalProcessingTime + " milliseconds");
+
+        try {
+            String thread1Response = future1.get();
+            assertTrue(thread1Response.equals("Hello"));
+
+            String thread2Response = future2.get();
+            assertTrue(thread2Response.equals("Beautiful"));
+
+            String thread3Response = future3.get();
+            assertTrue(thread3Response.equals("World"));
+
+        } catch (InterruptedException | ExecutionException e) {
+            e.printStackTrace();
+        }
+
+        WORKER_THREAD_POOL.shutdown();
+    }
+}

core-java/src/main/java/com/baeldung/java/nio/selector/EchoServer.java

@@ -13,6 +13,8 @@
 
 public class EchoServer {
 
+    private static final String POISON_PILL = "POISON_PILL";
+
     public static void main(String[] args) throws IOException {
         Selector selector = Selector.open();
         ServerSocketChannel serverSocket = ServerSocketChannel.open();
@@ -30,23 +32,36 @@ public static void main(String[] args) throws IOException {
                 SelectionKey key = iter.next();
 
                 if (key.isAcceptable()) {
-                    SocketChannel client = serverSocket.accept();
-                    client.configureBlocking(false);
-                    client.register(selector, SelectionKey.OP_READ);
+                    register(selector, serverSocket);
                 }
 
                 if (key.isReadable()) {
-                    SocketChannel client = (SocketChannel) key.channel();
-                    client.read(buffer);
-                    buffer.flip();
-                    client.write(buffer);
-                    buffer.clear();
+                    answerWithEcho(buffer, key);
                 }
                 iter.remove();
             }
         }
     }
 
+    private static void answerWithEcho(ByteBuffer buffer, SelectionKey key) throws IOException {
+        SocketChannel client = (SocketChannel) key.channel();
+        client.read(buffer);
+        if (new String(buffer.array()).trim().equals(POISON_PILL)) {
+            client.close();
+            System.out.println("Not accepting client messages anymore");
+        }
+
+        buffer.flip();
+        client.write(buffer);
+        buffer.clear();
+    }
+
+    private static void register(Selector selector, ServerSocketChannel serverSocket) throws IOException {
+        SocketChannel client = serverSocket.accept();
+        client.configureBlocking(false);
+        client.register(selector, SelectionKey.OP_READ);
+    }
+
     public static Process start() throws IOException, InterruptedException {
         String javaHome = System.getProperty("java.home");
         String javaBin = javaHome + File.separator + "bin" + File.separator + "java";

drools/backward-chaining/src/main/java/com/baeldung/drools/BackwardChaining.java

@@ -0,0 +1,33 @@
+package com.baeldung.drools;
+
+import org.kie.api.KieServices;
+import org.kie.api.runtime.KieContainer;
+import org.kie.api.runtime.KieSession;
+
+import com.baeldung.drools.model.Fact;
+import com.baeldung.drools.model.Result;
+
+public class BackwardChaining {
+    public static void main(String[] args) {
+        Result result = new BackwardChaining().backwardChaining();
+        System.out.println(result.getValue());
+        result.getFacts().stream().forEach(System.out::println);
+    }
+
+    public Result backwardChaining() {
+        Result result = new Result();
+        KieServices ks = KieServices.Factory.get();
+        KieContainer kContainer = ks.getKieClasspathContainer();
+        KieSession ksession = kContainer.newKieSession("ksession-backward-chaining");
+        ksession.setGlobal("result", result);
+        ksession.insert(new Fact("Asia", "Planet Earth"));
+//        ksession.insert(new Fact("China", "Asia"));
+        ksession.insert(new Fact("Great Wall of China", "China"));
+
+        ksession.fireAllRules();
+
+        return result;
+
+    }
+
+}

drools/backward-chaining/src/main/java/com/baeldung/drools/model/Fact.java

@@ -0,0 +1,69 @@
+package com.baeldung.drools.model;
+
+import org.kie.api.definition.type.Position;
+
+public class Fact {
+
+    @Position(0)
+    private String element;
+
+    @Position(1)
+    private String place;
+
+    public Fact(String element, String place) {
+        this.element = element;
+        this.place = place;
+    }
+
+    public String getElement() {
+        return element;
+    }
+
+    public void setElement(String element) {
+        this.element = element;
+    }
+
+    public String getPlace() {
+        return place;
+    }
+
+    public void setPlace(String place) {
+        this.place = place;
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((element == null) ? 0 : element.hashCode());
+        result = prime * result + ((place == null) ? 0 : place.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        Fact other = (Fact) obj;
+        if (element == null) {
+            if (other.element != null)
+                return false;
+        } else if (!element.equals(other.element))
+            return false;
+        if (place == null) {
+            if (other.place != null)
+                return false;
+        } else if (!place.equals(other.place))
+            return false;
+        return true;
+    }
+
+    @Override
+    public String toString() {
+        return "Fact{" + "element='" + element + '\'' + ", place='" + place + '\'' + '}';
+    }
+}