A Quick, but Important Improvement for Your Java Code

Dear all Java Developers, please stop doing this.

public void List<MyObject> getValues() {
    return new ArrayList(privateList);
}

Please start doing this instead.

public void Collection<MyObject> getValues() {
    return Collections.unmodifiableCollection(privateList);
}

Here are the reasons why.

1. Both List and Set are sub-interfaces of Collection, so both work. Forward ranges are better than random access ranges in most cases.
2. You will cut your memory usage by more than half for any object which has a method like this.
3. The resulting collection is immutable (though not transitively), so the return value cannot modify the collection you passed.
4. You’ll get an added guarantee that when passed down through several functions, the collection will be the same as when it was at the top.