[英]How can a child thread send continuous messages to main thread(method) in Java?
[英]How to return messages from child threads to main thread(method) in Java?
我有一個 HashMap 的人想互相交流如下:
{zidane=[rooney, rooney, rooney, scholes, rooney], rooney=[scholes, messi, scholes], scholes=[ronaldo], ronaldo=[rooney, messi, scholes], messi=[zidane]}
在這里,密鑰中的每個人都有自己的線程,他們將在其中向列表中的每個人發送消息並接收響應。
import java.util.*;
public class Master {
public Map callsMap = new HashMap<String, List>();
public static void main(String[] args){
Master m = new Master();
m.readFile();
Iterator<Map.Entry<String, List>> it = m.callsMap.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<String, List> pair = it.next();
String caller = pair.getKey();
List receiverList = pair.getValue();
SubTasks st = new SubTasks(caller, receiverList);
Thread thread = new Thread(st);
thread.start();
//st.getMessage();
}
}
}
master
class 將為 HashMap 中的每個鍵迭代創建一個線程。 請注意, readFile
方法只會從文本文件中讀取並生成我上面提到的輸入(到callsMap
變量中)。 這對於這種情況並不是特別重要,所以我在這里省略了它。
我有SubTasks
擴展了Thread
class 並為每個交互創建消息。 這個 class 不會創建任何額外的線程,而只是對它收到的調用者和接收者列表進行操作,如下所示:
import java.util.List;
public class SubTasks extends Thread {
private String caller;
private List receiverList;
private volatile String returnMessage;
SubTasks(String s, List l){
caller = s;
receiverList = l;
}
public void setMessage(String msg){
returnMessage = msg;
}
public String getMessage() {
return returnMessage;
}
@Override
public void run(){
for (int i = 0; i < receiverList.size(); i++) {
System.out.println(receiverList.get(i)+" received intro message from "+caller +" ["+System.currentTimeMillis()+"]");
returnMessage = caller+" received reply message from "+receiverList.get(i) +" ["+System.currentTimeMillis()+"]";
//setMessage(returnMessage);
System.out.println(returnMessage);
}
}
}
如果我在子線程中為所有 26 對打印消息,我會得到所需的 output。
zidane received message from messi [1592117172946]
rooney received message from ronaldo [1592117172946]
scholes received message from rooney [1592117172946]
rooney received message from zidane [1592117172946]
ronaldo received message from scholes [1592117172946]
messi received reply from zidane [1592117172989]
ronaldo received reply from rooney [1592117172989]
...
...
如何將這些消息傳遞到主線程(方法)並在那里打印而不是子線程? 我嘗試使用getter-setter
方法,但由於線程將隨機執行,因此無法正確調用getter
方法。
我建議你在你的用例中使用Executor
框架Callable
接口和Futures
,因為你需要的一切都已經解決了。 重寫 class 將幫助您正確解決它。
public class Master {
public Map callsMap = new HashMap<String, List>();
public static void main(String[] args){
Master m = new Master();
m.readFile();
ExecutorService executorService = Executors.newFixedThreadPool(10);// or some desired number
List<Future<String>> returnFutures = new ArrayList<>();
Iterator<Map.Entry<String, List>> it = m.callsMap.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<String, List> pair = it.next();
String caller = pair.getKey();
List receiverList = pair.getValue();
returnFutures.add(executorService.submit(new SubTasks(caller, receiverList) ));
}
executorService.shutdown();
while(executorService.awaitTermination(1000, TimeUnit.SECONDS));
for(Future<String> returnFuture: returnFutures){
/* returnFuture.get() will have the returned value from the thread, if the thread has completed execution,
otherwise it will wait for the completion*/
System.out.println(returnFuture.get());
}
}
}
和
public class SubTasks implements Callable<String> {
private String caller;
private List receiverList;
private volatile String returnMessage;
SubTasks(String s, List l){
caller = s;
receiverList = l;
}
public void setMessage(String msg){
returnMessage = msg;
}
public String getMessage() {
return returnMessage;
}
@Override
public String call (){
for (int i = 0; i < receiverList.size(); i++) {
System.out.println(receiverList.get(i)+" received intro message from "+caller +" ["+System.currentTimeMillis()+"]");
returnMessage = caller+" received reply message from "+receiverList.get(i) +" ["+System.currentTimeMillis()+"]";
return returnMessage;
}
}
}
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