Java: How ArrayList manages memory

Question

In my Data Structures class we have studies the Java ArrayList class, and how it grows the underlying array when a user adds more elements. That is understood. However, I ca

Answer 1

An ArrayList doesn't automatically shrink back, as far as i know. However, you can say something like:

ArrayList al = new ArrayList();

// fill the list for demo's sake
for (int i = 0; i < 1000000; ++i)
{
    al.add(i);
}

// now remove all but one element
al.removeRange(1, al.size());

// this should shrink the array back to a decent size
al.trimToSize();

Note, the amount of memory available probably won't change til the GC runs again.