Question

import java.io.*;
import javax.swing.JOptionPane;
import java.util.*;

public class lesson {
     static void printAll(ArrayList<String> names, int len)
      {
         Iterator it = names.iterator();
         while( it.hasNext() )
         {
         if( ((String)it.next()).length() == len)
         System.out.println( it.next() );
         }
      }
    public static void main(String[] args) throws IOException {
        ArrayList<String> names = new ArrayList<String>();
        names.add("Jan");
        names.add("Ivan");
        names.add("Tom");
        names.add("George");
        printAll(names,3);
    }
}

why is the output Ivan, George, shouldn’t it print only names with length 3 (which are Jan and Tom)?

Answer 1

if( ((String)it.next()).length() == len)
         System.out.println( it.next() );
         }

it.next() advances iterator to one element. You are doing it.next() twice.

if( ((String)it.next()).length() == len) advances one time and now iterator points to next()

Change it to something like below:

 it.next() prints next() element in iterator.
      {
       //Get once.
        String nextName = (String)it.next();
         if( nextName .length() == len)
         System.out.println(nextName  );
       }