How to check whether element is in the array in java?

Question

        int[] a = new int[5];
        a[0] = 5;
        a[1] = 2;
        a[2] = 4;
        a[3] = 12;
        a[4] = 6;
        int k = 2;
        if (k in a) { // whats's wrong here?
            System.out.println("Yes");
        }
        else {
            System.out.println("No");
        }

Thanks!

why are you calling `int[]` a list? Its an array, not a list. List means something else in Java — Sarwar Erfan, Mar 14 '11 at 18:26
dup http://stackoverflow.com/questions/1128723/in-java-how-can-i-test-if-an-array-contains-a-certain-value — AlfaTeK, Mar 14 '11 at 18:29

score 6 · Accepted Answer · edited Mar 14 '11 at 18:28

6

The "foreach" syntax in java is:

for (int k : a) { // the ':' is your 'in'
  if(k == 2){ // you'll have to check for the value explicitly
    System.out.println("Yes");
  }
}

edited Mar 14 '11 at 18:28

Paŭlo Ebermann

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answered Mar 14 '11 at 18:27

McStretch

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@Paŭlo - Thanks for the edit. I definitely did not notice that 'if' when I copied over his expression. – McStretch Mar 14 '11 at 18:30

score 1 · Answer 2 · answered Mar 14 '11 at 18:28

1

You have to do the search yourself. If the list were sorted, you could use java.util.arrays#binarySearch to do it for you.

answered Mar 14 '11 at 18:28

Ted Hopp

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Chris K · Answer 3 · 2011-03-14T19:21:06.360

0

If using java 1.5+

List<Integer> l1 = new ArrayList<Object>(); //build list 

for ( Integer i : l1 ) {  // java foreach operator 
  if ( i == test_value ) { 
      return true; 
  } 
} 
return false;

edited Mar 14 '11 at 19:21

answered Mar 14 '11 at 18:27

Chris K

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1) Can't have primitives in a list. 2) It's List, not list. 3) You can't instantiate a List because it's an interface not a class. – GriffeyDog Mar 14 '11 at 19:03
You would probably want List in this case. Downvote retracted. – GriffeyDog Mar 14 '11 at 19:17

score 0 · Answer 4 · answered Mar 14 '11 at 18:28

0

What's wrong? The compiler should say you that there is no in keyword.

Normally you would use a loop here for searching. If you have many such checks for the same list, sort it and use binary search (using the methods in java.util.Arrays).

answered Mar 14 '11 at 18:28

Paŭlo Ebermann

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score 0 · Answer 5 · answered Mar 14 '11 at 18:29

Instead of taking array you can use ArrayList. You can do the following

ArrayList list = new ArrayList();
list.add(5);
list.add(2);
list.add(4);
list.add(12);
list.add(6);
int k = 2;
if (list.contains(k) { 
    System.out.println("Yes");
}
else {
    System.out.println("No");
}

score 0 · Answer 6 · answered Mar 14 '11 at 18:29

You will need to iterate over the array comparing each element until you find the one that you are looking for:

// assuming array a that you defined.
int k = 2;
for(int i = 0; i < a.length; i++)
{
    if(k == a[i])
    {
        System.out.println("Yes");
        break;
    }
}

How to check whether element is in the array in java?

6 Answers6