class CallerThread1 implements Callable { public String call() throws Exception { return "thread";}}
class CallerThread2 implements Callable { public void call() {}}
class CallerThread3 extends Callable { public void call() throws IOException {}}
class CallerThread4 implements Callable { public String call(String s) { return "thread";}}
class CallerThread5 extends Callable { public void callable(String s) throws Exception {}}