Gain insights into Java Collections Framework. Delve into lists, sets, and hashmaps. Learn about data modification, sorting, thread-safety, and internal workings for efficient usage.

Collection is one of the most important topics for Java programming. Without the proper knowledge of every collection type in Java, it becomes difficult for you to decide which option to pick in a particular scenario.

This course will give you a great understanding of all collection types available in the Collections Framework like lists, linked lists, sets, and hashmaps. 

After completing this course, you will know how data can be modified within a collection, how to sort a collection, and how it can be made thread-safe. You will also cover the internal working of each Java collection so you can work with them more efficiently.

Collections in Java

## Problem: Find duplicate element

 You are given an array in which all the elements are unique except one element. You need to find the duplicate element. 

For example, the array is {12, 34, 1, 56, 43, 34, 65}

The output should be 34 since it is the only duplicate element.

This problem should be done in $O(n)$ complexity, and the array is not sorted.

# Problem: Find duplicate element

 You are given an array in which all the elements are unique except one element. You need to find the duplicate element. 

For example, the array is {12, 34, 1, 56, 43, 34, 65}

The output should be 34 since it is the only duplicate element.

This problem should be done in $O(n)$ complexity, and the array is not sorted.

Let's Begin

Lists in Java

LinkedList in Java

CopyOnWriteArrayList in Java

Sets in Java

TreeSet in Java

HashMap In Java

TreeMap in Java

LinkedHashMap in Java

Additional Map Implementations

Arrays Class

Collections Class

HashSet: Exercise

Problem: Find duplicate element