first commit

.gitignore

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+.idea/
+out/
+*.iml

src/Main.java

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+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.FutureTask;
+
+public class Main {
+
+    public static void main(String[] args) throws ExecutionException, InterruptedException {
+
+        // ***************** manual
+        Future<Integer> f = new FutureTask<>(() -> {
+            System.out.println("toto");
+            return 1;
+        });
+
+        showState(f);
+        ((FutureTask<Integer>) f).run();
+
+
+        // ***************** with pool
+        int nbProcs = Runtime.getRuntime().availableProcessors();
+        ExecutorService exec = Executors.newFixedThreadPool(nbProcs);
+        Future f2 = exec.submit(() -> {
+            try {
+                Thread.sleep(5000);
+            } catch (InterruptedException e) {
+                System.out.println("failed to sleep");
+            }
+        });
+
+        showState(f2);
+
+        System.out.println("Hello World!");
+    }
+
+    /**
+     * show state of future callback
+     * @param f
+     * @throws InterruptedException
+     * @throws ExecutionException
+     */
+    private static void showState(Future<Integer> f)
+        throws InterruptedException, ExecutionException {
+        System.out.println("is cancel : " + f.isCancelled());
+        System.out.println("is done : " + f.isDone());
+        System.out.println(f.get());
+    }
+}