My name
is
Jon Skeet

Why do I get an ArrayStoreException in Java?

My question is, why do I get an Exception in thread "main" java.lang.ArrayStoreException :

at java.lang.System.arraycopy (native method) at java.util.ArrayList.toArray (unknown source) at Main.main (Main.java:50)

Here's my code :

import java.io.*;
import java.util.*;

public class Main {

static public boolean readPinsData(File dataFile, ArrayList<Integer> data) {
   boolean err = false;
   try {
      Scanner scanner = new Scanner(dataFile);
      String line;
      while (scanner.hasNext()) {
         line = scanner.nextLine();
         try {
            data.add(Integer.parseInt(line));
         } catch (NumberFormatException e) {
            e.printStackTrace();
            err = true;
         }
      }
      scanner.close();
   } catch (FileNotFoundException e) {
      e.printStackTrace();
      err = true;
   }

   return err;
}


public static void main(String[] args) {
    Console console = System.console();
    int pinSize = 0;

    do{
    char passwordArray[] = console.readPassword("Enter pin: ");
    pinSize = passwordArray.length;

    if(pinSize != 4){
            System.out.println("Pin must be 4 digits");
        } else {
            System.out.println("Checking...");
        }


    ArrayList<Integer> pins = new ArrayList<Integer>();
   readPinsData(new File("bdd.txt"), pins);
   //System.out.println(pins);
   //System.out.println(passwordArray);

   String[] thePins = pins.toArray(new String[pins.size()]);
   String passEntered = String.valueOf(passwordArray);
   int i = 0;

   for(i = 0 ; i < thePins.length ; i++){
      if(passEntered == thePins[i]){
          System.out.println(":)");
      }else{
          System.out.println(":(");
      }
  }

   }while(pinSize != 4);

}
}

My bdd.txt file looks like :

Basically you've got a List<Integer> and you're trying to store the contents of it in a String[]. You can't do that. If you want to convert each Integer into a String, you'll need to do that explicitly.

For example:

String[] thePins = new String[pins.size()];
for (int i = 0; i < thePins.length; i++) {
    thePins[i] = pins.get(i).toString();
}

Or build a List<String> instead of using an array.

Or don't bother converting everything to a string collection at all - instead, just iterate over pins and test that way.

As noted by JB Nizet, you should also use equals rather than == when comparing strings.

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