java 笔记 ： 多线程处理–runnable & callable

1. runnable interface – this interface could be called by Thread() or ExecutorService

import static org.junit.Assert.*;

import java.util.Random;

import org.junit.Test;


public class Test_runnable {

	@Test
	public void test() throws InterruptedException {
		System.out.println("Begin Test!");
		int nThreadCnt=15;
		Thread[] threads = new Thread[nThreadCnt];
		for (int i=0;i<nThreadCnt;i++) {
			Thread t = new Thread(new Job(i));
			threads[i] = t;
			//if here use t.run(), then it will be
			//synchronised call, the main thread will
			//wait till the thread end, so here we should
			//use t.start();
			t.start();
		}
		Boolean bAllComplete=false;
		while(!bAllComplete) {
			bAllComplete = true;
			for (int i=0;i<nThreadCnt;i++) {
				if (threads[i].isAlive()) {
					bAllComplete = false;
					Thread.yield();
					break;
				}
			}
		}
		System.out.println("End Test!");
	}

}

class Job implements Runnable {

	@Override
	public void run() {
		System.out.println("Begin job " + this.id);
		Thread.yield();
		for (int i=0;i<seed;i++) {
			System.out.printf("Job id=%d, seed= %d of %d\n"
					, this.id, i+1, this.seed);
			Thread.yield();//give other thread opportunities to run
		}
		System.out.println("End job " + this.id);
	}
	public Job(int id) {
		this.id = id;
	}
	private int id ;
	private int seed =Math.abs((new Random()).nextInt()) % 10;
}

2. callable interface – callable must use ExecutorService to run it

import static org.junit.Assert.*;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

import org.junit.Test;


public class Test_Callable {

	@Test
	public void test() throws InterruptedException, ExecutionException {
		System.out.println("Begin Test!");
		int nThreadCnt=15;
		List<Future<String>> result = new ArrayList<Future<String>>();
		ExecutorService service = Executors.newCachedThreadPool();
		for (int i=0;i<nThreadCnt;i++) {
			result.add(service.submit(new CallableJob(i)));
		}
		//shutdown() will wait all the task to complete first
		service.shutdown();
		for (int i=0;i<nThreadCnt;i++) {
			System.out.println("The result of task " + i + " is " + result.get(i).get());
		}
		System.out.println("End Test!");
	}

}

class CallableJob implements Callable<String> {

	public CallableJob(int id) {
		this.id = id;
	}
	private int id ;
	private int seed =Math.abs((new Random()).nextInt()) % 10;
	@Override
	public String call() throws Exception {
		System.out.println("Begin job " + this.id);
		Thread.yield();
		for (int i=0;i<seed;i++) {
			System.out.printf("Job id=%d, seed= %d of %d\n"
					, this.id, i+1, this.seed);
			Thread.yield();//give other thread opportunities to run
		}
		System.out.println("End job " + this.id);
		return String.format("%s", this.seed);
	}
}

BTW, when using executor, and we wanna wait all the threads to end

, use awaitTermination() after shutdown()

		//shutdown() will wait all the task to complete first 		

　　　　　　　　service.shutdown(); 		

　　　　　　　　while(!service.awaitTermination(20, TimeUnit.MILLISECONDS)) { 			

　　　　　　　　　　System.out.println("Waiting end......."); 		

　　　　　　　　} 		

　　　　　　　　System.out.println("End Test!");