While loop not working properly. ArrayIndexOutOfBoundsException

Question

My while loop conditions doesn't seem to be working, i tried doing the condition with < and <= and it still doesn't work keeps on giving me the outofbounds error when i enter something that cannot be found. It works fine when I enter something that can be found but when it can't be found it goes to an outofbounds error

the error message is this

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 20

Code:

public static void main(String[] args) {
    int listsize;
    int[] listTosearch = new int[20];
    int elementTofind;
    boolean found = false;
    int indexToSearch;
    int indexOfelementTofind = -1;

    Scanner myScanner   = new  Scanner(System.in);
    System.out.println("Size of list to search?");
    listsize = myScanner.nextInt();

    for (int i = 0; i <= listsize - 1; i++){
        listTosearch[i] = 1 + (int) (Math.random()*(100-1)+1);
        System.out.println(listTosearch[i]);

    }
    System.out.println("Element to find?");
    elementTofind = myScanner.nextInt();
    indexToSearch = 0;

    while (indexToSearch < listsize -1 || found == false){ // This is the line that isn't working
        if (listTosearch[indexToSearch] == elementTofind ){
            found = true;
            indexOfelementTofind = indexToSearch + 1 ;
        }
        indexToSearch ++;
    }

    if (found == true){
        System.out.println(elementTofind + " is at index " + indexOfelementTofind);
    } else {
        System.out.println("The element was not found");
    }
}

Which line causes the exception? Please mark line that throws exception in your code snippet. — AlexR
– AlexR, Commented Mar 23, 2014 at 11:05

dting · Accepted Answer · 2014-03-23 11:53:15Z

3

while (indexToSearch < listsize -1 || found == false){

should be:

while (indexToSearch < listsize -1 && found == false){

or as peter.petrov pointed out:

while (indexToSearch < listsize && !found)

to actually search your entire array.

You might also consider making your code more readable by changing:

for (int i = 0; i <= listsize - 1; i++){

to

for (int i = 0; i < listsize; i++){

This is also somewhat strange:

    if (listTosearch[indexToSearch] == elementTofind ){
        found = true;
        indexOfelementTofind = indexToSearch + 1 ;
    }

and makes this misleading:

System.out.println(elementTofind + " is at index " + indexOfelementTofind);

since the element was found is at index indexToSearch not indexToSearch + 1

public static void main(String[] args) {
  Scanner myScanner   = new  Scanner(System.in);

  System.out.println("Size of list to search?");
  int listSize = myScanner.nextInt();

  int[] listToSearch = new int[listSize];
  for (int i = 0; i < listSize; i++) {
    listToSearch[i] = 1 + (int) (Math.random()*(100-1)+1);
    System.out.println(listToSearch[i]);   
  }

  System.out.println("Element to find?");
  int elementToFind = myScanner.nextInt();

  int index = 0;
  boolean found = false;
  while (index < listSize && !found) { 
    if (listToSearch[index] == elementToFind) {
      found = true;
    } else {
      index++;
    }
  }

  if (found) {
    System.out.println(elementToFind + " is at index " + index);
  } else {
    System.out.println("The element was not found");
  }
}

edited Mar 23, 2014 at 11:53

answered Mar 23, 2014 at 11:07

dting

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1 Comment

peter.petrov Over a year ago

Shouldn't it be: while (indexToSearch < listsize && !found) ?

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