Java return index if value found in array

Question

I am trying to find a value in an array and I know for sure that this value will exist only once, so i am trying to find the value and return the index of the array where it is stored, if not found return -1 This is what I am trying to do:

static Integer[] accs = new Integer[20];
 public static int search()
    {
        Integer[] numbers;
        numbers = accs;
        Integer key;
        Scanner sc = new Scanner(System.in);
         System.out.println("Enter the Account Number:");        
         key = sc.nextInt();

        for (Integer index = 0; index < numbers.length; index++)
      {
           if ( numbers[index] == key )
                 return index;  //We found it!!!
      }
     // If we get to the end of the loop, a value has not yet
     // been returned.  We did not find the key in this array.
     return -1;

    }

When I run this even though I know that the value exists in the array, nothing is being displayed. I debugged and then I found out that the Key variable is not having the value of what I typed. Is something wrong there?

Is there any reason you are using Integer rather than int ? What do you see in key and what were you expecting? — Peter Lawrey
– Peter Lawrey, Commented Aug 22, 2012 at 7:59
You're using == for object comparison (which does reference comparison). You should use equals, or simple int. This code will only accidentally work when your numbers are in the Integer cache range — zeller
– zeller, Commented Aug 22, 2012 at 7:59
Use equals instead of == to compare integers. Or use int instead. — assylias
– assylias, Commented Aug 22, 2012 at 7:59
you are comparing Integer objects by reference. You need to use equals — dcernahoschi
– dcernahoschi, Commented Aug 22, 2012 at 7:59

jolivier · Accepted Answer · 2016-03-06 00:33:53Z

7

Your array is storing Integer, which is a java Object, to test for equality of Java Object you need to call Object.equals method instead of ==.

In your case I suggest you use an array of int instead of Integer, it is lighter in memory, support == and you are not using any of the features of Integer so you don't need them here.

edited Mar 6, 2016 at 0:33

answered Aug 22, 2012 at 8:00

jolivier

7,7553 gold badges31 silver badges47 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

amit · Accepted Answer · 2012-08-22 08:00:26Z

4

You are checking for identity when checking with operator== (Are the two references point to the exact same object?) and not equality (do they equal each other?).

You should use ints (rather then Integers) or change the condition to use the equals() method.

answered Aug 22, 2012 at 8:00

amit

179k27 gold badges245 silver badges348 bronze badges

Comments

Jaco Van Niekerk · Accepted Answer · 2012-08-22 08:00:09Z

2

Integer is an object, so you have to make use of the equals method. Try numbers[index].equals(key).

answered Aug 22, 2012 at 8:00

Jaco Van Niekerk

4,2022 gold badges25 silver badges50 bronze badges

Comments

Ilya · Accepted Answer · 2012-08-22 08:02:01Z

1

java.util.Arrays.asList(accs).indexOf(key)

or

org.apache.commons.lang.ArrayUtils.indexOf(accs, key);

answered Aug 22, 2012 at 8:02

Ilya

29.9k19 gold badges119 silver badges161 bronze badges

Comments

Andreas Fester · Accepted Answer · 2012-08-22 08:01:41Z

0

Make sure you understand the difference between object equality and object identity. You are using "==" to check if your value is in the array - this checks for identity, not for equality. Use numbers[index].equals(key) instead.

answered Aug 22, 2012 at 8:01

Andreas Fester

36.8k9 gold badges101 silver badges125 bronze badges

Comments

user1616299 · Accepted Answer · 2012-08-22 08:16:37Z

0

You need set value for each element before search. The statement below only declare new array with 20 element with value = null static Integer[] accs = new Integer[20]; Replace by: static Integer[] accs = new Integer[]{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}; and retest.

Regards,

answered Aug 22, 2012 at 8:16

user1616299

1

Comments

mssb · Accepted Answer · 2012-08-22 08:23:41Z

0

initialize the array like this way static Integer[] accs = {3,5,15,6,4,32,9}; and call search() method in the main. your function work properly.

answered Aug 22, 2012 at 8:23

mssb

8781 gold badge8 silver badges19 bronze badges

Comments

Dhanushka Gunasinghe · Accepted Answer · 2012-08-22 10:15:51Z

0

Use following command for capture user input BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

answered Aug 22, 2012 at 10:15

Dhanushka Gunasinghe

11 bronze badge

Collectives™ on Stack Overflow

Java return index if value found in array

8 Answers 8

Comments

Comments

Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

8 Answers 8

Comments

Comments

Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related