In Java, when defining lists or maps, there is a syntax style that uses two sets of curly braces, {{ ... }}, known as Double Brace Initialization. First, take a look at this writing style, which makes ...

Eclipse Collections is a collections framework for Java with optimized data structures and a rich, functional and fluent API.

2.Define an interface-like class NestedInteger that can represent either a single integer or a nested list. 3.Use a stack or recursion to flatten all integers from the nested list into a single list.