英文:
Java while(true) loop never ends without a System.out.println
问题
我有以下代码，其中包含一个ArrayList，该ArrayList在另一个Java类中填充，该类是一个线程（我每次都检查，它总是被填充的），然后在主类中有有问题的**while(true)**代码块，问题是如果我注释或删除**System.out.println(IDS.size());**这一行，它永远不会结束。
尽管线程负责完成我需要的信息，但在它们全部完成之前，我不能显示结果。这就是使用while(true)的原因。
// 这个ArrayList在其他类中被正确地填充（每个线程都会添加一个元素，总共10个）
public static ArrayList<String> IDS = new ArrayList<String>();
// 这里是问题所在
while (true) {
// 如果我注释掉下面的system.out.println这一行
// 循环将永远不会结束，也不会中断
System.out.println(IDS.size());
if (IDS.size() == 10) {
break;
}
}
// 当数组填充有10个元素时，我显示所有信息
for (int k = 0; k < impresoras.size(); k++) {
System.out.println(impresoras.get(k).ID);
}
我不知道为什么会出现这种情况，有人能帮忙吗？
提前谢谢。
英文:
I have the following code with an ArrayList that is filled in other Java class that is a Thread (this is always filled, I have checked every time), then I have in the Main class the problematic block while(true) and the issue is that never ends if I comment or delete the line System.out.println(IDS.size());
Although are Threads in charge of complete the information I need, I cant show the results until all of them are finished. This is the reason of while(true) block.
public static ArrayList<String> IDS = new ArrayList<String>();
//this arraylist is filled in other classes correctly (each Thread add a element -> 10 in total)
//here is the problem
while (true) {
//if I comment the next system.out.println line
//the loop never ends and never breaks
System.out.println(IDS.size());
if(IDS.size()==10) {
break;
}
}
//when the array is filled with the 10 elements, I show all the info
for (int k = 0; k < impresoras.size(); k++) {
System.out.println(impresoras.get(k).ID);
}
I don´t know why this is happening, can someone helps?
Thanks in advance.
答案1
得分: 0
最后，我使用线程的join方法来避免使用while true循环。所以，我只需调用next方法，然后在所有线程完成工作后执行System.out.println来打印我的项目，这些项目将在所有线程结束工作时打印出来。
public static ArrayList<MyThread> threadList = new ArrayList<MyThread>();
public static void openFileAndCreateThreads(String fileName) {
String line = null;
FileReader fileReader = null;
BufferedReader bufferedReader = null;
try {
fileReader = new FileReader(fileName);
bufferedReader = new BufferedReader(fileReader);
while ((line = bufferedReader.readLine()) != null) {
String[] line_parts = line.split(";");
MyThread t = new MyThread(line_parts[0].trim(), line_parts[1], line_parts[2]);
threadList.add(t);
t.start();
}
for (int j = 0; j < threadList.size(); j++) {
try {
threadList.get(j).join();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
bufferedReader.close();
} catch (FileNotFoundException ex) {
ex.printStackTrace();
} catch (IOException ex) {
ex.printStackTrace();
} finally {
try {
bufferedReader.close();
} catch (Exception ex) {
}
}
}
英文:
Finally I use the join methods for the Threads to avoid the while true loop.
So only I have to call the next method and then do the System.out.println of my items, that will be printed when all Threads ends their work.
public static ArrayList<MyThread> threadList = new ArrayList<MyThread>();
public static void openFileAndCreateThreads(String fileName) {
String line = null;
FileReader fileReader = null;
BufferedReader bufferedReader = null;
try {
fileReader = new FileReader(fileName);
bufferedReader = new BufferedReader(fileReader);
while ((line = bufferedReader.readLine()) != null) {
String[] line_parts = line.split(";");
MyThread t= new MyThread(line_parts[0].trim(), line_parts[1], line_parts[2]);
threadList.add(t);
t.start();
}
for (int j=0;j<threadList.size();j++) {
try {
threadList.get(j).join();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
bufferedReader.close();
} catch (FileNotFoundException ex) {
ex.printStackTrace();
} catch (IOException ex) {
ex.printStackTrace();
} finally {
try {
bufferedReader.close();
} catch (Exception ex) {
}
}
}
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