Better way to find index of item in ArrayList?

ArrayList<String> alphabetList = new ArrayList<String>();
alphabetList.add("A"); // 0 index
alphabetList.add("B"); // 1 index
alphabetList.add("C"); // 2 index
alphabetList.add("D"); // 3 index
alphabetList.add("E"); // 4 index
alphabetList.add("F"); // 5 index
alphabetList.add("G"); // 6 index
alphabetList.add("H"); // 7 index
alphabetList.add("I"); // 8 index

int position = -1;
position = alphabetList.indexOf("H");
if (position == -1) {
    Log.e(TAG, "Object not found in List");
} else {
    Log.i(TAG, "" + position);
}

Output: List Index : 7

If you pass H it will return 7, if you pass J it will return -1 as we defined default value to -1.

Done


ArrayList has a indexOf() method. Check the API for more, but here's how it works:

private ArrayList<String> _categories; // Initialize all this stuff

private int getCategoryPos(String category) {
  return _categories.indexOf(category);
}

indexOf() will return exactly what your method returns, fast.


If your List is sorted and has good random access (as ArrayList does), you should look into Collections.binarySearch. Otherwise, you should use List.indexOf, as others have pointed out.

But your algorithm is sound, fwiw (other than the == others have pointed out).