threads callable

java/threads/src/main/java/com/bejond/threads/callable/ReturnWithResultThread.java

@@ -0,0 +1,23 @@
+package com.bejond.threads.callable;
+
+import java.util.concurrent.Callable;
+
+/**
+ * Created by bejond on 4/16/16.
+ *
+ * If we want a thread return a value, we can make the thread implement
+ * Callable<T>.
+ */
+public class ReturnWithResultThread implements Callable {
+	private long id;
+
+	public ReturnWithResultThread(long id) {
+		this.id = id;
+	}
+
+	@Override
+	public Object call() throws Exception {
+		System.out.println("Invoke call()" + id);
+		return "The thread return result is " + id;
+	}
+}

java/threads/src/test/java/com/bejond/threads/callable/TestReturnWithResultThread.java

@@ -0,0 +1,54 @@
+package com.bejond.threads.callable;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+/**
+ * Created by bejond on 4/16/16.
+ */
+public class TestReturnWithResultThread {
+
+	@Test
+	public void testReturnThread() {
+
+		/**
+		 * Executors.newCachedThreadPool() returns a ThreadPoolExecutor instance,
+		 * ThreadPoolExecutor extends AbstractExecutorService, and
+		 * AbstractExecutorService implements ExecutorService.
+		 */
+		ExecutorService executorService = Executors.newCachedThreadPool();
+
+		ArrayList<Future<String>> futureArrayList =
+			new ArrayList<Future<String>>();
+
+		for (int i = 0; i < 100; i++) {
+
+			/**
+			 * AbstractExecutorService implements submit(Callable<T>).
+			 * submit() invoke call().
+			 */
+			futureArrayList.add(
+				executorService.submit(new ReturnWithResultThread(i)));
+		}
+
+		System.out.println("Adding threads is done.");
+
+		for (Future<String> future : futureArrayList) {
+			try {
+				// get() blocks until completing task
+				System.out.println(future.get());
+			} catch (InterruptedException e) {
+				e.printStackTrace();
+			} catch (ExecutionException e) {
+				e.printStackTrace();
+			} finally {
+				executorService.shutdown();
+			}
+		}
+	}
+}