Finding if an array contains all elements in another array

Question

I am trying to loop through 2 arrays, the outer array is longer then the other. It will loop through the first and if the 2nd array does not contain that int it will return

Answer 1

If you would like to use contains then you need an ArrayList. See: http://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html#contains(java.lang.Object)

Otherwise, you need two loops.

There is a workaround like this:

public boolean linearIn(int[] outer, int[] inner) {
    List innerAsList = arrayToList(inner);
    for (int i = 0; i < outer.length; i++) {
      if (!innerAsList.contains(outer[i])) {
         return false;
      }
   }
   return true;
}  

private List arrayToList(int[] arr) {
    List result= new ArrayList(arr.length);
    for (int i : arr) {
        result.add(i);
    }
    return result;
}

But don't think that looping is not happening, just because you don't see it. If you check the implementation of the ArrayList you would see that there is a for loop: http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/util/ArrayList.java#ArrayList.indexOf(java.lang.Object) So you are not gaining any performance. You know your model best, and you might be able to write more optimized code.