Using Runnable to run a method by multiple threads

[mahmood.n]

In my program, I want to create multiple threads in one of the methods where each thread has to run a specific method with a given input. Using Runnable, I have written this snippet.

class myClass {
  public myClass() { }
  public void doProcess() {
    List< String >[] ls;
    ls = new List[2];  // two lists in one array
    ls[0].add("1");  ls[0].add("2");  ls[0].add("3");
    ls[1].add("4");  ls[1].add("5");  ls[1].add("6");

    // create two threads 
    Runnable[] t = new Runnable[2]; 
    for (int i = 0; i < 2; i++) {
      t[ i ] = new Runnable() {
        public void run() {
          pleasePrint( ls[i] );
        }
      };
      new Thread( t[i] ).start();
    }
  }
  void pleasePrint( List< String > ss )
  {
    for (int i = 0; i < ss.size(); i++) {
      System.out.print(ss.get(i)); // print the elements of one list
    }
  }
}

public class Threadtest {
  public static void main(String[] args) {
    myClass mc = new myClass();
    mc.doProcess();
  }
}

Please note, my big code looks like this. I mean in one method, doProcess(), I create an array of lists and put items in it. Then I want to create threads and pass each list to a method. It is possible to define the array and lists as private class members. But, I want to do that in this way.

Everything seems to be normal, however, I get this error at calling pleasePrint():

error: local variables referenced from an inner class must be final or effectively final
      pleasePrint( ls[i] );

How can I fix that?

[Norm]

variables referenced from an inner class must be final or effectively final

Did you try making ls final? What happened?