import java.util.ArrayList;
import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;

public class Book {
	public Book() {
		ArrayList<FutureTask<String>> mFutures = new ArrayList<FutureTask<String>>();

		for (int i = 0; i < 6; i++) {
			TestThread thread = new TestThread(i);
			FutureTask<String> futureTask = new FutureTask<>(thread);
			mFutures.add(futureTask);

			new Thread(futureTask).start();
		}

		for (FutureTask<String> task : mFutures) {
			try {
				System.out.println(task.get());
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
	}

	private class TestThread implements Callable<String> {
		private int id;

		public TestThread(int id) {
			this.id = id;
		}

		@Override
		public String call() {
			System.out.println("线程:" + id + " -> 运行...");

			try {
				Thread.sleep(5000);
			} catch (Exception e) {
				e.printStackTrace();
			}

			System.out.println("线程:" + id + " -> 结束.");

			return "返回的字符串" + id;
		}
	}

	public static void main(String[] args) {
		new Book();
	}
}

Log output：

线程:2 -> 运行...
线程:3 -> 运行...
线程:0 -> 运行...
线程:5 -> 运行...
线程:4 -> 运行...
线程:1 -> 运行...
线程:0 -> 结束.
线程:5 -> 结束.
线程:4 -> 结束.
线程:1 -> 结束.
线程:2 -> 结束.
线程:3 -> 结束.
返回的字符串0
返回的字符串1
返回的字符串2
返回的字符串3
返回的字符串4
返回的字符串5