Thread之四：java线程返回结果的方法

两种方式：一种继承Thread类实现；一种通过实现Callable接口。

第一种方法：

因为实现Thread类的run方法自身是没有返回值的，所以不能直接获得线程的执行结果，但是可以通过在run方法里把最后的结果传递给实例变量，然后通过getXX方法获取该实例变量的值。继承实现的代码：

package com.dxz.thread;
 
import java.util.Random;
import java.util.concurrent.TimeUnit;
 
class RunThread extends Thread {
    private String runLog = "";
    private String name;
 
    public RunThread(String name) {
        this.name = name;
    }
 
    public void run() {
        try {
            int time = new Random().nextInt(10);
            System.out.println("sleep "+ time +" second.");
            TimeUnit.SECONDS.sleep(time);
            this.runLog = this.name + time;
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
 
    public String getRunLog() {
        return this.runLog;
    }
}
package com.dxz.thread;
public class RunThreadTest {
 
    public static void main(String[] args) throws InterruptedException {
        RunThread runT = new RunThread("world");
        runT.start();
        runT.join();
        System.out.println("result:="+runT.getRunLog());
 
    }
 
}

结果：

sleep 3 second.
result:=world3

结果2：

sleep 2 second.
result:=world2

第二种方法：

继承Callable接口后需要实现call方法，而call方法默认是可以有返回值的，所以可以直接返回想返回的内容。接口的实现代码：

package com.dxz.thread;
 
import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;
 
class CallThread implements Callable<String> {
    private String runLog = "";
    private String name;
 
    public CallThread(String name) {
        this.name = name;
    }
    @Override
    public String call() throws Exception {
        try {
            int time = new Random().nextInt(10);
            System.out.println("sleep " + time + " second.");
            TimeUnit.SECONDS.sleep(time);
            this.runLog = this.name + time;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return runLog;
    }
}

调用类：

package com.dxz.thread;
 
import java.util.ArrayList;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
 
public class CallThreadTest {
 
    public static void main(String[] args) throws ExecutionException {
        String result = "";
        ExecutorService exs = Executors.newCachedThreadPool();
        ArrayList<Future<String>> al = new ArrayList<Future<String>>();
        al.add(exs.submit(new CallThread("hello")));
        al.add(exs.submit(new CallThread("world")));
        for (Future<String> fs : al) {
            try {
                result += fs.get() + ",";
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.println("result:="+result);
    }
 
}

结果：

sleep 5 second.
sleep 3 second.
result:=hello3,world5,

 更多介绍见《Runnable、Callable、Future和FutureTask用法》