java中多线程的并行执行
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Parallel Execution of multiple threads in java
提问by user907810
I have to execute multiple instances of my class concurrently. i have written the following code below. I have done it in two ways. But I don't see the difference. What is the right way to have parallel running threads?
我必须同时执行我的类的多个实例。我在下面编写了以下代码。我已经通过两种方式做到了。但我看不出有什么区别。并行运行线程的正确方法是什么？
Thanks.
谢谢。
Here the snippet:
这里的片段：
public class MyClass {
public MyClass() {
runnable = true;
}
public boolean isRunnable() {
return runnable;
}
public static void main(String[] args) throws InterruptedException {
/* METHOD 1
MyClass myclass = new MyClass();
if (myclass.isRunnable()) {
for (int i = 0; i < loop; i++) {
myclass.execTask();
Thread.sleep(sleep);
}
}
*/
//METHOD 2
final MyClass myclass = new MyClass();
ExecutorService threadPool = Executors.newFixedThreadPool(threadNo);
for (int i = 0; i < threadNo; i++) {
threadPool.submit(new Runnable() {
public void run() {
for (int i = 0; i < loop; i++) {
myclass.execTask();
try {
Thread.sleep(sleep);
} catch (InterruptedException ex) {
Logger.getLogger(MyClass.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
});
}
threadPool.shutdown();
public void execTask(){
.........
}
}
}
回答by Charles Forsythe
The difference between your two methods is that in "Method 2," you may actually have multiple threads of execution (assuming that threadNois greater than 1). Method 2 allows for multiple work threads to grab a Runnableand call execTask(by calling run) in parallel (concurrently, to be precise). The pause in "Method 2" does pretty much nothing.
您的两种方法之间的区别在于，在“方法 2”中，您实际上可能有多个执行线程（假设threadNo大于 1）。方法 2 允许多个工作线程并行（准确地说是并发）获取 aRunnable并调用execTask（通过调用run）。“方法 2”中的停顿几乎没有任何作用。
"Method 1" executes entirely on the "Main" thread. It calls execTask, waits, and then calls it again. This will call the execution some number of times serially.
“方法 1”完全在“主”线程上执行。它调用execTask，等待，然后再次调用它。这将连续多次调用执行。
(I assume this is pseudo-code because parts of it won't compile.)
（我认为这是伪代码，因为它的一部分无法编译。）
Here is a cleaned-up "Method 2". Note that I have threadNoworker threads (it helps if this is larger than 1) and I create loopRunnables.
这是一个清理过的“方法2”。请注意，我有threadNo工作线程（如果它大于 1，它会有所帮助）并且我创建了loopRunnables.
ExecutorService threadPool = Executors.newFixedThreadPool(threadNo);
for (int i = 0; i < loop; i++) {
threadPool.submit(new Runnable() {
public void run() { myclass.execTask(); });
}
