Get number of duplicates from ArrayList

Question

For example, say I have an ArrayList that could contain the following values:

x
x
x
y
y

Now what I want to retrieve is the number

Answer 1

Check out the Multiset in google guava: http://docs.guava-libraries.googlecode.com/git-history/v11.0.2/javadoc/com/google/common/collect/Multiset.html

Example:

Multiset strings = HashMultiset.create(arrayList);
int countX = strings.count("x"); // the count of x

More examples can be found on the Guava wiki.