I need unique elements without losing their first-appearance order. *Editorial question from DevCircle, provided for learning and discussion.*

Calling a method on an optional value throws NullPointerException. How can I avoid this? *Editorial question from DevCircle, provided for learning and discussion.*

I need a list with frequent reads and occasional insertions. How do the implementations differ? *Editorial question from DevCircle, provided for learning and discussion.

Why does the compiler require handling some exceptions but not others? *Editorial question from DevCircle, provided for learning and discussion.*

Two String objects contain the same text, but comparing them with == can return false. *Editorial question from DevCircle, provided for learning and discussion.*