Callable和Future
Callable和Future
Callable和Future，它俩很有意思的，一个产生结果，一个拿到结果。
Callable接口类似于Runnable，从名字就可以看出来了，但是Runnable不会返回结果，并且无法抛出返回结果的异常，而Callable功能更强大一些，被线程执行后，可以返回值，这个返回值可以被Future拿到，也就是说，Future可以拿到异步执行任务的返回值，
public class Test extends Object{
/**
* @param args
*/
public static void main(String[] args) {
ExecutorService threadPool = Executors.newCachedThreadPool();
final CompletionService<Integer> cs = new ExecutorCompletionService<Integer>(threadPool);
for(int i = 1; i < 5; i++) {
final int taskID = i;
cs.submit(new Callable<Integer>() {
public Integer call() throws Exception {
Thread.sleep(1000);
return taskID;
}
});
}
System.out.println(" ***");
new Thread(){
public void run(){
// 可能做一些事情
for(int i = 1; i < 5; i++) {
try {
System.out.println(cs.take().get());
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
}
}.start();
System.out.print(" pong");
}
void c(){
ExecutorService threadPool = Executors.newSingleThreadExecutor();
Future<Integer> future = threadPool.submit(new Callable<Integer>() {
public Integer call() throws Exception {
Thread.sleep(1000);
return new Random().nextInt(100);
}
});
future = threadPool.submit(new Callable<Integer>() {
public Integer call() throws Exception {
Thread.sleep(1000);
int i=new Random().nextInt(100);
System.out.println(i);
return i;
}
});
future = threadPool.submit(new Callable<Integer>() {
public Integer call() throws Exception {
Thread.sleep(1000);
return new Random().nextInt(100);
}
});
System.out.print(" pong");
}
void b(){
for(int i=0;i<5;i++){
Callable<String> c = new Callable<String>(){
public String call() throws Exception {
Thread.currentThread().sleep(2000);
System.out.println("call");
return String.valueOf(new Random().nextInt(100));
}
};
FutureTask<String> future = new FutureTask<String>(c);
new Thread(future).start();
try {
Thread.currentThread().sleep(1000);
String s;
s = future.get();
System.out.println(s);
}
catch (InterruptedException e) {
System.out.println("**1**");
e.printStackTrace();
}catch (ExecutionException e) {
e.printStackTrace();
}
}
System.out.print(" pong");
}
void a(){
//int i=0,j,k=0;
//for(j=0;i<6 && j<10;i++,j++){
//k=i+j;
//}
//System.out.println("i="+i + ",j="+j);
Callable<String> c = new Callable<String>(){
public String call() throws Exception {
Thread.currentThread().sleep(2000);
System.out.println("call");
return String.valueOf(new Random().nextInt(100));
}
};
FutureTask<String> future = new FutureTask<String>(c);
new Thread(future).start();
try {
Thread.currentThread().sleep(1000);
String s;
s = future.get();
System.out.println(s);
}
catch (InterruptedException e) {
System.out.println("**1**");
e.printStackTrace();
}catch (ExecutionException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
/*new Thread(){
public void run() {
System.out.print("ping");
}
}.start();
try {
Thread.currentThread().sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.print(" pong");
*/
System.out.print(" pong");
}
}