Abstract A collection of pre-written classes and interfaces provided by Oracle Corporation as part of the Java Development Kit (JDK) java.util.* Package in Java that provides a collection of Data Structure and Algorithm, not automatically imported java.util.TreeSet Hash Map but with elements sorted, the time complexity is O(logn) for insertion, deletion, search. O(n) to list all elements in a sorted manner java.util.Arrays For Arrays.sort(), the elements inside the Array must be a type of Object. int[] can’t, because int is a Primitive Datatype java.util.ArrayDeque Doesn’t support null elements, but LinkedList can java.lang.* Core package in Java that is automatically imported into every Java program
