Thread: ArrayIndexOutOfBoundsException...Help!!

I'm writing an array program that has the user input a series of integers, and the program has to count how many duplicates of a number are entered if any and output the data in increasing order..I almost have it but I am stuck trying to figure out why I am getting an out of bounds error for the loop in the numSame function...What am I doing wrong? When It doesn't give the out of bounds error, the counter isn't tallying how many duplicates there are...It always outputs zero..my sample data is 12,34,56,78,12,34,56,78

 
import java.util.*;
 
public class arrayProgram{
    static Scanner console = new Scanner(System.in);
 
 
   public static void main(String[] args)
 {   
 
		int[] numList = new int[100];
		int[] listCopy = new int[100];
		int[] numCount = new int[100];
 
 
   	 	readData(numList);
			copyList(numList,listCopy);
			numSame(numList,listCopy,numCount);
			Arrays.sort(numList);
			for(int num=0;num<numList.length;num++)
			{
			  System.out.println("Look--->  " + numList[num]);
 
			}
      }
 
 
    public static void readData(int[] list)
    {
	  	int i;
 
	  	System.out.print("Enter a series of positive integers: ");
 
            for (i = 0; i < list.length; i++){
		 list[i] = console.nextInt();
		  if (list[i] == -999)
		   break;}
 
         System.out.println();
    }
 
 
	     public static void copyList(int list[], int list2[])
    {
		int index;
 
		for (index = 0; index < list.length; index++)
		   { list2[index]=list[index];
		     System.out.println(list2[index]);}
 
    }
 
	    public static void numSame(int[] list1, int[] list2, int[] list3) 
                       {
		                 int counter = 0;
		                 int k = 0;
                                                for(int i : list1)
                                                          {
								  for(int j : list2)
								  {
								     if(list1[i] == list2.length)
									  {      counter++;
									     list3[k] = counter;
									      k++;
 
									  }
								  }
 
 
								}
                       System.out.println("Counter :  " + counter);
 
         }
      }

Originally Posted by Norm

When you get an error, please copy the full text of the error message and paste it here. It has valuable info about the problem.

Sorry,
Here is the error:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -999
at arrayProgram.numSame(arrayProgram.java:70)
at arrayProgram.main(arrayProgram.java:21)

The -999 is supposed to be a sentinel controlled loop...It's supposed to end the input from the user, but I don't know why it's being used in the program like it is...

Originally Posted by Norm

That is a very strange index value: -999
Do you recognize where that came from? Why is the code trying to use that for an index?

Look at line 70 and see why the code was using -999 for an index.




Can you explain in detail what the logic of the program is? What are all the large arrays for? Is their size related to the data that is entered?

--- Update ---

I'm supposed to assume that the data set has at most 100 numbers, and -999 marks the end of the input data...

I have 3 arrays...The numList array accepts input values from the console. The 2nd array listCopy has the values from the numList array deep copied into it...I did that so I could use it to compare with the numList array to see how many duplicate numbers are entered...The 3rd array numSame, is supposed to hold the values of the number of duplicates...I use Arrays.sort to print out the numbers in increasing order...I understand everything that's going on except the error I'm getting...It keeps saying out of bounds on the line where the variable 'counter' is attempting to assign it's value to list3[k] ...it's somethings about the third array...I'm stumped..

Originally Posted by Norm

Use this code to print out the array so you can see what is in it:

System.out.println("an ID "+ java.util.Arrays.toString(theArrayNameHere));

Use the name of your array.

What you posted were the requirements, not a description of the program's logic.
Given the requirements for the program, now you need to do some design work and decide what steps the program needs to take to do it.
Before working on the code any more, make a list of the steps the code needs to take and what variables will be needed to work with.

Originally Posted by 112297

I have 3 arrays...The numList array accepts input values from the console. The 2nd array listCopy has the values from the numList array deep copied into it...I did that so I could use it to compare with the numList array to see how many duplicate numbers are entered...The 3rd array numSame, is supposed to hold the values of the number of duplicates...I use Arrays.sort to print out the numbers in increasing order...I understand everything that's going on except the error I'm getting...It keeps saying out of bounds on the line where the variable 'counter' is attempting to assign it's value to list3[k] ...it's somethings about the third array...I'm stumped..

The program outputs zero because the numSame method is calling the 3 arrays you declared at the start. In other words, they're empty, so your if-statement is evaluating whether 0 equals the array length (100).

Why not just search for duplicates directly from the numList array? Instead of checking for duplicates, the numSame method increments a counter if values from 1 array equal the length of another array, where both arrays have the same length. The third array stores values from the counter, which I'm not understanding the reason for. Your program isn't complete and I suggest you lay out the logic, then start over.