Java：如何使用 Thread.join
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Java: How to use Thread.join
提问by Nick Heiner
I'm new to threads. How can I get t.jointo work, whereby the thread calling it waits until t is done executing?
我是线程的新手。我怎样才能开始t.join工作，从而调用它的线程等待 t 完成执行？
This code would just freeze the program, because the thread is waiting for itself to die, right?
这段代码只会冻结程序，因为线程正在等待自己死亡，对吗？
public static void main(String[] args) throws InterruptedException {
Thread t0 = new Thready();
t0.start();
}
@Override
public void run() {
for (String s : info) {
try {
join();
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.printf("%s %s%n", getName(), s);
}
}
What would I do if I wanted to have two threads, one of which prints out half the infoarray, then waits for the other to finish before doing the rest?
如果我想要两个线程，其中一个打印出info数组的一半，然后等待另一个完成，然后再执行其余操作，我该怎么办？
采纳答案by Francis Upton IV
Use something like this:
使用这样的东西：
public void executeMultiThread(int numThreads)
throws Exception
{
List threads = new ArrayList();
for (int i = 0; i < numThreads; i++)
{
Thread t = new Thread(new Runnable()
{
public void run()
{
// do your work
}
});
// System.out.println("STARTING: " + t);
t.start();
threads.add(t);
}
for (int i = 0; i < threads.size(); i++)
{
// Big number to wait so this can be debugged
// System.out.println("JOINING: " + threads.get(i));
((Thread)threads.get(i)).join(1000000);
}
回答by user85421
You have to call the joinmethod on the other Thread.
Something like:
您必须join在另一个线程上调用该方法。
就像是：
@Override
public void run() {
String[] info = new String[] {"abc", "def", "ghi", "jkl"};
Thread other = new OtherThread();
other.start();
for (int i = 0; i < info.length; i++) {
try {
if (i == info.length / 2) {
other.join(); // wait for other to terminate
}
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.printf("%s %s%n", getName(), info[i]);
}
}
回答by Sven Lilienthal
With otherThread being the other thread, you can do something like this:
将 otherThread 作为另一个线程，您可以执行以下操作：
@Override
public void run() {
int i = 0;
int half = (info.size() / 2);
for (String s : info) {
i++;
if (i == half) {
try {
otherThread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.printf("%s %s%n", getName(), s);
Thread.yield(); //Give other threads a chance to do their work
}
}
The Java-tutorial from Sun: http://java.sun.com/docs/books/tutorial/essential/concurrency/join.html
Sun 的 Java 教程：http: //java.sun.com/docs/books/tutorial/essential/concurrency/join.html
