How can I find objects that are in BOTH arrays and promptly add it to another array?

Question

How can I create a method that recieve two arrays as parameters and return an array filled with the items that were in both arrays?

Input (Array1 passed in method): ["Lisa", "George", "Mario"] Input (Array2 passed in method): ["Luigi", "Susan", "Lisa"]

Method should return: ["Lisa"]

I cannot use any built in methods so I have to build my own algorithm, but I'm stuck for the past 2 hours. How can I achieve this in Java?

Edit: Christ on a candle stick. It's not for homework. I'm just real shitty at algorithms. Especially ones as basic as this, and especially on a foreign language I've never used. :P

Answer 1

One quick way is the following algorithm:

For each item in list1, add it to a dictionary.
For each item in list2, check if it exists in dictionary, 
if item exists, add it to list3
else continue.
return list3.

Answer 2

Brute force.

Loop over the first array. Inside that loop, have another over the second array. Compare entries from both, adding them to a new array if you get a match.

Answer 3

    [] result = ...

    foreach( itemA in a ) {
        foreach(  iteamB in b ) {
             if( itemB == itemA ) { // if they are in both places
                   r[] = itemB // append it to the result
             }
         }
    }
    return result;

Answer 4

How about:

private static String[] findCommon(final String[] array1,
        final String[] array2) {
    final Set<String> common = new HashSet<String>();
    common.addAll(Arrays.asList(array1));
    common.retainAll(Arrays.asList(array2));
    return common.toArray(new String[0]);
}