I need Help

[Wolfgang Obi]

I've been tinkering at this programme for a while now, but i seem not to be making any more progress,....

the programme is supposed to ask for integers from the command line until "stop" is entered,....and then give out which integers were entered and how many of each integer were read in....

whene�ver i incorporate the part containing the Array "elementsCorrected" i always get a number format exception thrown out! why is that?

here are my programme code pieces, where am i going wrong?

thanx!

  
 
import java.util.* ;
 

public class EnterStop{
 
 /** This method receives the Array from parse() and counts how </br>
 *   many of each element are to be found in it.
 *   The result is printed to the screen.
 *
 * @param noah
 *
 */
 
         public void elementCheck(int[] noah){
              int count =0;
              int i;
              Arrays.sort(noah);
              int markedElement = noah[0];
              for(i = 0;i < noah.length;i++) {
                  if(markedElement !=  noah[i]){
                   System.out.println
                   (markedElement+" occurs "+count+" times");
                     markedElement = noah[i];
                     count = 0;
                  }
                   count ++;
              }
              System.out.println(markedElement+" occurs "+count+" times");
        }//elementCheck
 
/** This method creates a string Array from the entries made from the command line by the user.</br>
*   Entries are read into the Array until "stop" is entered.
* @return elements
* @see createArray#equalsIgnoreCase
*/
 
       public String[] createArray(){
            String[] elements = new String[5];
            String number;
            int zaehler = 0;
            int incr = 3;
 
            //int i = 0;
            do{
               System.out.print
               ("What is your "+(zaehler + 1)+". integer?: " );
               number = IM.readString();
               if(zaehler>= elements.length)
                  elements = enlargeArray(elements, incr);
               if(number.equalsIgnoreCase("STOP")) break;
               elements[zaehler] = number;
               zaehler ++;
            }while(true);
 
            /*
            int h = i;
            String[] elementsCorrected = new String[h];
 
            for(int j = 0; j <  h ; j++){
                elementsCorrected[j] = elements[j];
            }
            return elementsCorrected;
            */
 

 

           /*
            for(int i=0; i < elements.length; i++){
 
                  System.out.print("What is your "+(i+1)+". integer?: " );
                  String number = IM.readString();
 
                  if(number.equalsIgnoreCase("STOP")){
 
                       int h = i;
                       String[] elementsCorrected = new String[h];
 
                       for(int j = 0; j <  h ; j++){
                           elementsCorrected[j] = elements[j];
 
                       }
                       return elementsCorrected;
                   }else{
 
                      elements[i] = number;
 
                   }
             }
             */
 
             return elements;
        }//createArray
 

/** This method parses the complete elements of the string Array to int elements,</br>
*   and reloads them into an int Array.
* @param sammy
* @see parse#parseInt
* @return elements2
*/
         public int[] parse(String[] elements){
            int[] elements2 = new int[elements.length];
            for(int i=0; i < elements.length; i++){
               //System.out.println(i);
              elements2[i] = Integer.parseInt(elements[i]);
              //return elements2;
             }
            return elements2;
         }
 
/**  This method enlarges the Array if more elements than oldArray.length are entered */
  
       public String[] enlargeArray(String[] oldArray, int incr){
 
            String[] newArray = new String[(oldArray.length ) + incr];
            for(int j = 0; j < oldArray.length ; j++){
                newArray[j] = oldArray[j];
            }
            return newArray;
         }
 

 
 /** This method is called up to provide information on the function of this class*/
 
 public void progInfo(){
             System.out.println();
             System.out.println
             ("******************************************************************");
             System.out.println
             ("Program: ............................ ");
             ("*******************************************************************");
             System.out.println();
   }
 
/** This is the main method of the class */
 
         public static void main(String[] noah){
            /*String[] ir = createArray();      //TEST: Input/Output
            for(int i = 0; i < ir.length; i++){
               System.out.println(ir[i]);
            }*/
 
               EnterStop test5 = new EnterStop();
               test5.progInfo();
               test5.elementCheck(test5.parse(test5.createArray()));
         }
}
 

 
  

[Campbell Ritchie]

Your enlargeArray method means there are always more spaces in the array than there are members. So one of the elements will be null. Hence the NumberFormatException.

CR

[marc weber]

Instead of "enlarging" an array (making a new array that's bigger, and then moving each element over), you should really consider an ArrayList. You might think of an ArrayList as an array that automatically re-sizes itself.

I know that you've asked about ArrayLists in another thread, so I'm curious why you're using an array. Are you required to use an array here? Do you have more questions about using an ArrayList?

import java.util.List;
import java.util.ArrayList;
import java.util.ListIterator;
 
class ArrayListDemo {
  public static void main(String[] args) {
    List<String> myList = new ArrayList<String>();
    myList.add("abc");
    myList.add("ghi");
    myList.add(1, "def");
    myList.add("jkl");
    System.out.println("List size: " + myList.size());
    System.out.println(myList);
    System.out.println("String at 2: " + myList.get(2));
    System.out.println("Index of def: " + myList.indexOf("def"));
    
    ListIterator it = myList.listIterator();
    while(it.hasNext()) {
      System.out.println("Iterating: " + it.next());
    }
    
    System.out.println("Removing items...");
    myList.remove(2);
    myList.remove("abc");
    System.out.println("List size: " + myList.size());
    System.out.println(myList);
  }
}

[Michael Dunn]

if you don't want to use an arraylist, here's a way for you to get your input
into an undetermined-length array.

Don't think it's real efficient, but might suit.

    
public class Testing
{
  String[] array;
  public Testing()
  {
    array = createAndLoadArray();
    printArray();
  }
  public String[] createAndLoadArray()
  {
    StringBuffer sb = new StringBuffer();
    while(true)
    {
      String line = simulateReadConsole();
      if(line.equalsIgnoreCase("STOP")) break;
      sb.append(line+"|");
    }
    return sb.toString().split("\\|");
  }
  public String simulateReadConsole()
  {
    int number = (int)(Math.random()*10);
    if(number == 7) return "STOP";
    return String.valueOf(number);
  }
  public void printArray()
  {
    for(int x = 0; x < array.length; x++)
    {
      System.out.println(array[x]);
    }
  }
  public static void main(String[] args){new Testing();}
}

[Wolfgang Obi]

@Campbell Ritchie...
I took care of this using this(see code):

   
if(number.equalsIgnoreCase("STOP")){ 
 int h = i;
 String[] elementsCorrected = new String[h];                        
 for(int j = 0; j <  h ; j++){
  elementsCorrected[j] = elements[j]
 }
  return elementsCorrected;
 

but thanx anyway.

@marc weber....
thanks for the ArrayList explanation. This is exactly what i was looking for, that notwithstanding i think solving the problem "manually" with Arrays first will help me understand the solution with ArrayLists better(dont u think?)....

@Michael Dunn....
wonderful!...you really helped me there.

I've solved the problem! *GGG*

thanx all!

[Campbell Ritchie]

Mark Weber is right about the ArrayList.

I don't think h = i actually sorts out your problem. Using i when number.equals("STOP") still gives you an out-by-one error. Hence the Exception.

[Wolfgang Obi]

Originally posted by Campbell Ritchie:
Mark Weber is right about the ArrayList.

I don't think h = i actually sorts out your problem. Using i when number.equals("STOP") still gives you an out-by-one error. Hence the Exception.

hmm,...
okay, lets go through this then:

lets take an array of 5 elements as example....
( e.g.: String[] elements = new String[5]; )

then we begin with the entries.....

1st entry: x1 -> position in Array : "0"
2nd entry: x2 -> position in Array : "1"
3rd entry: "STOP" -> position in Array: "2"

now this is done:
h = i; ....
then: String[] elementsCorrected = new String[h];

then we do:
elementsCorrected[j] = elements[j]
"elements" is now an Array with (h = 2) elements...
---> (for 0 <= J < h ) !!!

in any case it did work for me....however: only when i did this afterwards:

elements = elementsCorrected; break; (and voila! NO NullPointer or number excepions )

as against:

return elementsCorrected;...as commented in my earlier post (still dont know why though :/ )

but it worked *lol*
[ June 01, 2006: Message edited by: Wolfgang Obi ]