Fehler beim Erstellen meiner ArrayList Thread-Safe. Ausnahme im Thread "main" java.lang.ClassCastException: Was ist falsch?

Question

Ich entschied mich, das untenstehende Codeelement zu optimieren, stieß aber auf Probleme. Ich habe versucht, die ArrayList in thread-sichere Sammlung zu ändern, indem Sie this discussion verwenden, aber leider ging etwas schief. Der Code kompiliert, aber löst die Ausnahme aus.

Exception in thread "main" java.lang.ClassCastException: java.util.Collections $ SynchronizedRandomAccessList kann nicht auf java.util.ArrayList bei bfpasswrd_multi.PasswordCracker.doItMulti (PasswordCracker.java:73) gegossen werden bei bfpasswrd_multi.PasswordCracker.runMulti (PasswordCracker.java:60) bei bfpasswrd_multi.Test.main (Test.java:16)

Bitte, sagen Sie mir, was ist falsch?

---

package bfpasswrd_multi; 

import java.util.ArrayList; 
import java.util.Collections; 
import java.util.concurrent.ExecutorService; 
import java.util.concurrent.Executors; 
import java.util.concurrent.Future; 


public class PasswordCracker 
{ 

String passwordToCrack; 
public boolean passwordFound; 
int min; 
int max; 
StringBuffer crackedPassword; 

public void prepare(String text) 
{ 
    passwordToCrack = text; 

    passwordFound = false; 
    min = 48; 
    max = 57;        // http://ascii.cl/ 
    crackedPassword = new StringBuffer(); 
    crackedPassword.append((char) (min - 1));   
} 

public void result() 
{ 
    System.out.println("Cracked Password is: " + crackedPassword.toString()); 
} 

public void incrementString(StringBuffer toCrack, int min, int max) 
{ 
    toCrack.setCharAt(0, (char) ((int) toCrack.charAt(0) + 1)); 
    for (int i = 0; i < toCrack.length(); i++) 
    { 
     if (toCrack.charAt(i) > (char) max) 
     { 
      toCrack.setCharAt(i, (char) min); 
      if (toCrack.length() == i + 1) 
      { 
       toCrack.append((char) min); 
      } 
      else 
      { 
       toCrack.setCharAt(i + 1, (char) ((int) toCrack.charAt(i + 1) + 1)); 
      } 
     } 
    } 
} 

public void runMulti(String text) 
{ 
    prepare(text); 
    double time = System.nanoTime(); 
    doItMulti(); 
    time = System.nanoTime() - time; 
    System.out.println(time/(1000000000)); 
    result(); 

} 


public void doItMulti() 
{ 
    int cores = Runtime.getRuntime().availableProcessors(); 
    ArrayList<Future<?>> tasks ;   // How do I make my ArrayList Thread-Safe? Another approach to problem in Java? 
             // https://stackoverflow.com/questions/2444005/how-do-i-make-my-arraylist-thread-safe-another-approach-to-problem-in-java 
    tasks = (ArrayList<Future<?>>) Collections.synchronizedList(new ArrayList<Future<?>>(cores)); 
    // ArrayList<Future<?>> tasks = new ArrayList<>(cores); 
    ExecutorService executor = Executors.newFixedThreadPool(cores); 
    final long step = 2000; 
    for (long i = 0; i < Long.MAX_VALUE; i += step) 
    { 
     while(tasks.size() > cores) 
     { 
      for(int w = 0; w < tasks.size();w++) 
      { 
       if(tasks.get(w).isDone()) 
       { 
        tasks.remove(w); 
        break; 
       } 
      } 
      try 
      { 
       Thread.sleep(0); 
      } 
      catch (InterruptedException e) 
      { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } 
     } 
     { 
      final long j = i; 
      if (passwordFound == false) 
      { 
       tasks.add(executor.submit(new Runnable() 
       { 

        public void run() 
        { 
         long border = j + step; 
         StringBuffer toCrack = new StringBuffer(10); 
         toCrack.append(constructString3(j, min, max)); 
         for (long k = j; k < border; k++) 
         { 
          incrementString(toCrack, min, max); 
          boolean found = toCrack.toString().equals(passwordToCrack); 
          if (found) 
          { 
           crackedPassword = toCrack; 
           passwordFound = found; 
           break; 
          } 
         } 
        } 
       })); 
      } 
      else 
      { 
       break; 
      } 
     } 
    } 
    executor.shutdownNow(); 
} 

public String constructString3(long number, long min, long max) 
{ 

    StringBuffer text = new StringBuffer();   
    if (number > Long.MAX_VALUE - min)    
    { 
     number = Long.MAX_VALUE - min;    
    }             

    ArrayList<Long> vector = new ArrayList<Long>(10); 
    vector.add(min - 1 + number); 
    long range = max - min + 1; 
    boolean nextLetter = false; 
    for (int i = 0; i < vector.size(); i++) 
    { 
     long nextLetterCounter = 0; 
     while (vector.get(i) > max) 
     { 
      nextLetter = true; 
      long multiplicator = Math.abs(vector.get(i)/range); 
      if ((vector.get(i) - (multiplicator * range)) < min) 
      { 
       multiplicator -= 1; 
      } 
      vector.set(i, vector.get(i) - (multiplicator * range)); 
      nextLetterCounter += multiplicator; 
     } 
     if (nextLetter) 
     { 
      vector.add((long) (min + nextLetterCounter - 1)); 
      nextLetter = false; 
     } 
     text.append((char) vector.get(i).intValue()); 
    } 
    return text.toString(); 
} 
} 

Vielen Dank im Voraus!

Answer 1

Die Frage, die Sie sehen, sind mit dieser Linie ist:

tasks = (ArrayList<Future<?>>) Collections.synchronizedList(new ArrayList<Future<?>>(cores)); 

Collections.synchronizedList keine ArrayList zurückkehrt; es gibt eine Unterklasse von List - java.util.Collections$SynchronizedRandomAccessList um genau zu sein - und ich weiß nichts über diese Klasse außer es ist ein List, aber es ist kein ArrayList.

Die einfache Lösung ist tasks zu erklären, ein List<Future<?>> zu sein:

List<Future<?>> tasks = 
    Collections.synchronizedList(new ArrayList<Future<?>>(cores)); 

Answer 2

Liebe Community Mitglieder danken Sie für Ihre Kommentare. Es scheint, dass jetzt meine Safethread-Liste funktioniert. Für die Leute, die in der Lösung interessant sind, werde ich den aufgelösten Code unten vorlegen. Auch sollte ich erwähnen, dass ich umbenennen Aufgabe zu Futures, bitte beachten Sie. Noch einmal vielen Dank!

package bfpasswrd_multi; 

import java.util.ArrayList; 
import java.util.Collections; 
import java.util.List; 
import java.util.concurrent.ExecutorService; 
import java.util.concurrent.Executors; 
import java.util.concurrent.Future; 


public class PasswordCracker 
{ 

String passwordToCrack; 
public boolean passwordFound; 
int min; 
int max; 
StringBuffer crackedPassword; 

public void prepare(String text) 
{ 
    passwordToCrack = text; 

    passwordFound = false; 
    min = 48; 
    max = 57;        // http://ascii.cl/ 
    crackedPassword = new StringBuffer(); 
    crackedPassword.append((char) (min - 1));   
} 

public void result() 
{ 
    System.out.println("Cracked Password is: " + crackedPassword.toString()); 
} 

public void incrementString(StringBuffer toCrack, int min, int max) 
{ 
    toCrack.setCharAt(0, (char) ((int) toCrack.charAt(0) + 1)); 
    for (int i = 0; i < toCrack.length(); i++) 
    { 
     if (toCrack.charAt(i) > (char) max) 
     { 
      toCrack.setCharAt(i, (char) min); 
      if (toCrack.length() == i + 1) 
      { 
       toCrack.append((char) min); 
      } 
      else 
      { 
       toCrack.setCharAt(i + 1, (char) ((int) toCrack.charAt(i + 1) + 1)); 
      } 
     } 
    } 
} 

public void runMulti(String text) 
{ 
    prepare(text); 
    double time = System.nanoTime(); 
    doItMulti(); 
    time = System.nanoTime() - time; 
    System.out.println(time/(1000000000)); 
    result(); 

} 


public void doItMulti() 
{ 
    int cores = Runtime.getRuntime().availableProcessors(); 
    // ArrayList<Future<?>> task;   // HOW IT WAS 
              // 
    // tasks = (ArrayList<Future<?>>) Collections.synchronizedList(new ArrayList<Future<?>>(cores));     // HOW IT WAS 
    List<Future<?>> futures ;    // THE SOLUTION 
    futures = Collections.synchronizedList(new ArrayList<Future<?>>(cores));          // THE SOLUTION 


    // ArrayList<Future<?>> tasks = new ArrayList<>(cores); 
    ExecutorService executor = Executors.newFixedThreadPool(cores); 
    final long step = 2000; 
    for (long i = 0; i < Long.MAX_VALUE; i += step) 
    { 
     while(futures.size() > cores) 
     { 
      for(int w = 0; w < futures.size();w++) 
      { 
       if(futures.get(w).isDone()) 
       { 
        futures.remove(w); 
        break; 
       } 
      } 
      try 
      { 
       Thread.sleep(0); 
      } 
      catch (InterruptedException e) 
      { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } 
     } 
     { 
      final long j = i; 
      if (passwordFound == false) 
      { 
       futures.add(executor.submit(new Runnable() 
       { 

        public void run() 
        { 
         long border = j + step; 
         StringBuffer toCrack = new StringBuffer(10); 
         toCrack.append(constructString3(j, min, max)); 
         for (long k = j; k < border; k++) 
         { 
          incrementString(toCrack, min, max); 
          boolean found = toCrack.toString().equals(passwordToCrack); 
          if (found) 
          { 
           crackedPassword = toCrack; 
           passwordFound = found; 
           break; 
          } 
         } 
        } 
       })); 
      } 
      else 
      { 
       break; 
      } 
     } 
    } 
    executor.shutdownNow(); 
} 

public String constructString3(long number, long min, long max) 
{ 

    StringBuffer text = new StringBuffer();   
    if (number > Long.MAX_VALUE - min)    
    { 
     number = Long.MAX_VALUE - min;    
    }             

    ArrayList<Long> vector = new ArrayList<Long>(10); 
    vector.add(min - 1 + number); 
    long range = max - min + 1; 
    boolean nextLetter = false; 
    for (int i = 0; i < vector.size(); i++) 
    { 
     long nextLetterCounter = 0; 
     while (vector.get(i) > max) 
     { 
      nextLetter = true; 
      long multiplicator = Math.abs(vector.get(i)/range); 
      if ((vector.get(i) - (multiplicator * range)) < min) 
      { 
       multiplicator -= 1; 
      } 
      vector.set(i, vector.get(i) - (multiplicator * range)); 
      nextLetterCounter += multiplicator; 
     } 
     if (nextLetter) 
     { 
      vector.add((long) (min + nextLetterCounter - 1)); 
      nextLetter = false; 
     } 
     text.append((char) vector.get(i).intValue()); 
    } 
    return text.toString(); 
} 
}