[英]Multithreading Java- Threads clashing/overwriting issue
我使用一个简单的线程池读取大型词典,我编写了一个for循环,遍历整个词典(10000个单词),我试图将其存储,因此它将每500个存储到一个线程中,将该子数组列表分配给一个单线程处理。
当数组列表中有500个单词时,它将存储在“单词”类的实例中。 这只是存储并允许访问arrayList(分配给该线程的arrayList)。
这似乎不起作用,因为存在重复项,并且在大多数情况下,字典中的最后500个单词是所有线程最终使用的内容,我觉得很奇怪。 另外,我还注意到,当我在如下所示的for循环内部的末尾添加一个简单的超时3秒时,它可以工作,但这似乎是一个可怕的解决方法,我希望该程序尽可能高效和快速。
// Executor Program
ExecutorService executor = Executors.newFixedThreadPool(cores);
ArrayList<String> words123 = new ArrayList<String>();
for (int i = 0; i < dictionary.size(); i++) {
words123.add(dictionary.get(i));
if(words123.size() == 1000) {
Words wordsList = new Words(words123);
Runnable worker = new WorkerThread(wordsList, passwords, stp);
executor.execute(worker);
words123 = new ArrayList<String>();
}
}
executor.shutdown();
//wait for all jobs to complete
while (!executor.isTerminated()) {
}
System.out.println("Finished all threads");
// WORD OBJECT ------------------
public class Words {
public static ArrayList<String> words = new ArrayList<String>();
public Words(ArrayList words) {
this.words = words;
}
public int getSize() {
return words.size();
}
public String getWord(int i) {
return words.get(i);
}
}
//WORKER THREAD ----------------
public static Words wordList;
public static int cmd;
public static HashMap<String, String> passwords = new HashMap<String, String>();
public static SimpleThreadPool stp;
/**
* Constructor
* @param s
*/
public WorkerThread(Words word, HashMap passwords, SimpleThreadPool stp, int cmd){
this.wordList = word;
//System.out.println("in " + words);
//Read in hashes using readFromFile method
this.passwords = passwords;
this.stp = stp;
this.cmd = cmd;
}
/**
* For a thread pool to function, ensure that the run() method terminates
* This method prints out the command, calls a function, then prints end and terminates
*/
@Override
public void run() {
//System.out.println(Thread.currentThread().getName()+" Start.");
//System.out.println("WOOOO " + wordList.getWords() + cmd);
for(int i = 0; i < wordList.getSize(); i++){
Password pass = new Password(wordList.getWord(i), hashPassword(wordList.getWord(i)));
//System.out.println(pass.getOriginalPass());
//checkHash(pass);
// Check password with letter-number edits (e.g. a-->@)
letterSymbolEdit(pass);
// Check password with capital letter edits
//capitalsEdit(pass);
// Reverse password
reverseEdit(pass);
// Concatenate all words in dictionary
//concatEdit(pass);
printPermutations(pass);
// All possible numbers generated and appended to string
for(int j = 0; j < 4; j++){
numberBuilder("", 0, j, pass);
}
}
//System.out.println(Thread.currentThread().getName()+" End.");
}
问题在于Words类中的'words'变量是静态的,这意味着该类的每个实例都使用相同的列表。
另外,由于您试图提高效率,因此我将使用其他方法。 代替
ExecutorService executor = Executors.newFixedThreadPool(cores);
采用
LinkedBlockingQueue<Runnable> workQueue = new LinkedBlockingQueue<>();
ThreadPoolExecutor executor = new ThreadPoolExecutor(cores, cores, 0L, TimeUnit.MILLISECONDS, workQueue);
executor.prestartAllCoreThreads();
然后将Runnable实例直接添加到workQueue中。 这样,您不必等待自己在线程之间划分单词:线程将在完成任务后立即获取它们。
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