线程池提交任务的两种方式:execute与submit的区别
阅读原文时间:2023年07月08日阅读:1

Java中的线程池在进行任务提交时,有两种方式:execute和submit方法。

  • execute只能提交Runnable类型的任务,无返回值。submit既可以提交Runnable类型的任务,也可以提交Callable类型的任务,会有一个类型为Future的返回值,但当任务类型为Runnable时,返回值为null。
  • execute在执行任务时,如果遇到异常会直接抛出,而submit不会直接抛出,只有在使用Future的get方法获取返回值时,才会抛出异常。

测试代码:

package com.javaBase.LineDistancePond;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
* 〈一句话功能简述〉;
* 〈execute与submit的区别〉
*
* @author jxx
* @see [相关类/方法](可选)
* @since [产品/模块版本] (可选)
*/
public class TestThreadPoolBegin {

public static void main(String\[\] args) throws Exception{  
    ExecutorService es = Executors.newSingleThreadExecutor();  
    Runnable runnable = new Runnable() {  
        @Override  
        public void run() {  
            System.out.println("Runnable线程处理开始...");  
            int a = 0;  
            int b = 3;  
            System.out.println("除以0的结果为:" + b/a);  
            System.out.println("Runnable线程处理结束...");  
        }  
    };  
    es.execute(runnable);  
    es.shutdown();  
}  

}

执行结果:

Exception in thread "pool-1-thread-1" java.lang.ArithmeticException: / by zero
Runnable线程处理开始…
at com.javaBase.LineDistancePond.TestThreadPoolBegin$1.run(TestThreadPoolBegin.java:24)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

Process finished with exit code 0

package com.javaBase.LineDistancePond;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
* 〈一句话功能简述〉;
* 〈execute与submit的区别〉
*
* @author jxx
* @see [相关类/方法](可选)
* @since [产品/模块版本] (可选)
*/
public class TestThreadPoolBegin {

public static void main(String\[\] args) throws Exception{  
    ExecutorService es = Executors.newSingleThreadExecutor();  
    Runnable runnable = new Runnable() {  
        @Override  
        public void run() {  
            System.out.println("Runnable线程处理开始...");  
            int a = 0;  
            int b = 3;  
            System.out.println("除以0的结果为:" + b/a);  
            System.out.println("Runnable线程处理结束...");  
        }  
    };  
    es.submit(runnable);  
    es.shutdown();  
}  

}

执行结果:

Runnable线程处理开始…

Process finished with exit code 0

package com.javaBase.LineDistancePond;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

/**
* 〈一句话功能简述〉;
* 〈execute与submit的区别〉
*
* @author jxx
* @see [相关类/方法](可选)
* @since [产品/模块版本] (可选)
*/
public class TestThreadPoolBegin {

public static void main(String\[\] args) throws Exception{  
    ExecutorService es = Executors.newSingleThreadExecutor();  
    Callable callable = new Callable() {  
        @Override  
        public Object call() throws Exception {  
            System.out.println("线程处理开始...");  
            int a = 0;  
            int b = 3;  
            System.out.println("除以0的结果为:" + b/a);  
            System.out.println("线程处理结束...");  
            return "0";  
        }  
    };  
    Future<String> future = es.submit(callable);  
    System.out.println("任务执行完成,结果为:" + future.get());  
}  

}

执行结果:

Exception in thread "main" java.util.concurrent.ExecutionException: java.lang.ArithmeticException: / by zero
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:192)
at com.javaBase.LineDistancePond.TestThreadPoolBegin.main(TestThreadPoolBegin.java:32)
Caused by: java.lang.ArithmeticException: / by zero
at com.javaBase.LineDistancePond.TestThreadPoolBegin$1.call(TestThreadPoolBegin.java:26)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
线程处理开始…

future的get方法在未获得返回值之前会一直阻塞,我们可以使用future的isDone方法判断任务是否执行完成,然后再决定是否get,因此上述代码我们可以优化如下:

package com.javaBase.LineDistancePond;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

/**
* 〈一句话功能简述〉;
* 〈execute与submit的区别〉
*
* @author jxx
* @see [相关类/方法](可选)
* @since [产品/模块版本] (可选)
*/
public class TestThreadPoolBegin {

public static void main(String\[\] args) throws Exception{  
    ExecutorService es = Executors.newSingleThreadExecutor();  
    Callable callable = new Callable() {  
        @Override  
        public String call() throws Exception {  
            System.out.println("线程处理开始...");  
            int a = 2;  
            int b = 3;  
            System.out.println("3/2的结果为:" + b/a);  
            System.out.println("线程处理结束...");  
            return "0";  
        }  
    };  
    Future<String> future = es.submit(callable);  
    while(true) {  
        //idDone:如果任务已完成,则返回 true。 可能由于正常终止、异常或取消而完成,在所有这些情况中,此方法都将返回 true。  
        if(future.isDone()) {  
            System.out.println("任务执行完成:" + future.get());  
            break;  
        }  
    }  
    es.shutdown();  
}  

}

执行结果:

线程处理开始…
3/2的结果为:1
线程处理结束…
线程执行完成:0

Process finished with exit code 1