Java ArrayList contains amount?

Question

Is there any way to figure out how many of something an ArrayList contains? Let's say:

ArrayList list = new ArrayList(); list.add("Hi"); list.add("Hi"); list.add("Hi");

Now I want to be able to figure out how many "Hi"'s are in there.. any easy method or small codeblock to?

Answer 1

Collections.frequency . So in your example, Collections.frequency(list, "Hi");

Answer 2

标准JDK已经提供了完全做到这一点的Collections.frequency(Collection<?> c, Object o) 。