How do you subtract one array of chars from another in Java?

Question

Let's say I have an array, arrayA = ["a", "b", "c", "d", "e", "f"], and another array, arrayB = ["a", "d", "e"].

I want to subtract arrayB from arrayA to yield the result = ["b", "c", "f"]

This is my setup for each array:

char[] arrayA = new char[7];
for(char c = 'a'; c <= 'f'; ++c) {
    arrayA[c - 'a'] = c;
}
char[] arrayB = new char[]{'a','d','e'};

(Please excuse any improper use of symbols and syntax, I'm a Ruby noob trying to learn Java simply from the Oracle tutorials. Thanks!) edit: a word and quotes

Answer 1

The short answer is to convert your arrays to "sets", and then use set operations on them. I'm looking for the proper code for that right now, but you can start by checking out this post: Classical set operations for java.util.Collection

Edit: Luke657 brings up a good point. primitive arrays are weird. So below is the updated code:

Assuming you start with a char array (it would of course be better to start with a set, but oh well):

char[] arrayA = new char[] {'a', 'b', 'c', 'd', 'e', 'f'};
char[] arrayB = new char[] {'a', 'd', 'e'};
Character[] objarrayA = ArrayUtils.toObject(arrayA);
Character[] objarrayB = ArrayUtils.toObject(arrayB);
Set<T> setA = new HashSet(Arrays.asList(objarrayA));
Set<T> setB = new HashSet(Arrays.asList(objarrayB));

setA.removeAll(setB);

Then, to get it back to a char array:

Character[] result;
result = setA.toArray(result);
char[] cresult = ArrayUtils.toPrimitive(result);

I believe this will do what you need. The Arrays.asList() operation is O(1), so is efficient and not computationally expensive, so don't worry about that extra conversion.