The following editor will bring you a brief talk about the submit method of ThreadPoolExecutor thread pool. The editor thinks it is quite good, so I will share it with you now and give it as a reference for everyone. Let’s follow the editor and take a look.
##jdk1.7.0_79
In the previous article "ThreadPoolExecutor thread pool principle and its execute method", the principle of the thread pool ThreadPoolExecutor and its execute method were mentioned. This article analyzes ThreadPoolExecutor#submit.
For the execution of a task, sometimes we don’t need it to return results, but there are times when we need its return execution results. For a thread, if it does not need to return a result, it can implement Runnable, and if it needs to execute the result, it can implement Callable. In the thread pool, execute also provides a task execution that does not need to return results, and for those that need to return results, its submit method can be called.Review the inheritance relationship of ThreadPoolExecutor.
Only the execute method is defined in the Executor interface, while the submit method is defined in the ExecutorService interface.//ExecutorService public interface ExecutorService extends Executor { ... <T> Future<T> submit(Callable<T> task); <T> Future<T> submit(Runnable task, T result); <T> Future<T> submit(Runnable task); ... }
//AbstractExecutorService public abstract class AbstractExecutorService implements ExecutorService { ... public <T> Future<T> submit(Callable<T> task) { if (task == null) throw new NullPointerException(); RunnableFuture<T> ftask = newTaskFor(task); execute(ftask); return ftask; } public <T> Future<T> submit(Runnable task, T result) { if (task == null) throw new NullPointerException(); RunnableFuture<T> ftask = newTaskFor(task); execute(ftask); return ftask; } public Future<?> submit(Runnable task) { if (task == null) throw new NullPointerExeption(); RunnableFuture<Void> ftask = newTaskFor(task, null); execute(ftask); return ftask; } ... }
Below are three examples to get a feel for the submit method.
submit(Callablepackage com.threadpoolexecutor; import java.util.concurrent.*; /** * ThreadPoolExecutor#sumit(Callable<T> task) * Created by yulinfeng on 6/17/17. */ public class Sumit1 { public static void main(String[] args) throws ExecutionException, InterruptedException { Callable<String> callable = new Callable<String>() { public String call() throws Exception { System.out.println("This is ThreadPoolExetor#submit(Callable<T> task) method."); return "result"; } }; ExecutorService executor = Executors.newSingleThreadExecutor(); Future<String> future = executor.submit(callable); System.out.println(future.get()); } }
submit(Runnable task, T result)
package com.threadpoolexecutor; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; /** * ThreadPoolExecutor#submit(Runnable task, T result) * Created by yulinfeng on 6/17/17. */ public class Submit2 { public static void main(String[] args) throws ExecutionException, InterruptedException { ExecutorService executor = Executors.newSingleThreadExecutor(); Data data = new Data(); Future<Data> future = executor.submit(new Task(data), data); System.out.println(future.get().getName()); } } class Data { String name; public String getName() { return name; } public void setName(String name) { this.name = name; } } class Task implements Runnable { Data data; public Task(Data data) { this.data = data; } public void run() { System.out.println("This is ThreadPoolExetor#submit(Runnable task, T result) method."); data.setName("kevin"); } }
submit(Runnable task)
package com.threadpoolexecutor; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; /** * ThreadPoolExecutor#sumit(Runnable runnables) * Created by yulinfeng on 6/17/17. */ public class Submit { public static void main(String[] args) throws ExecutionException, InterruptedException { Runnable runnable = new Runnable() { public void run() { System.out.println("This is ThreadPoolExetor#submit(Runnable runnable) method."); } }; ExecutorService executor = Executors.newSingleThreadExecutor(); Future future = executor.submit(runnable); System.out.println(future.get()); } }
Object, T, and ?, please refer to "Object, T (generic), and ? Difference in Java").
As you can see from the source code above, these three methods are almost the same. The key lies in:RunnableFuture<T> ftask = newTaskFor(task); execute(ftask);
//AbstractExecutorService#newTaskFor protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) { return new FutureTask<T>(callable); } protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) { return new FutureTask<T>(runnable, value); }
The Future Mode in Java".
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