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

We have a **TreeMap** in which we need to store the stock data. The key is the company's name, and value is the price of the stock of that company.

By default, when we store the Map's stock data, it will be stored in sorted order by key. But we need to store the data such that it is sorted by value. This means that the first element will be the company with the lowest stock price, and the last element will be the company with the highest stock price.

We know that while creating a **TreeMap** object we can provide a **Comparator** implementation that will be used to sort the elements. We can write a **Comparator** implementation so that it sorts the elements based on  values instead of keys.

The below example shows how we can sort the elements on the basis of values. We have created a **Comparator** implementation that compares the values for the two keys passed to it.

> Please note that in the below implementation, we are returning 1 if both the values are the same. The reason for doing this is that if two values are the same, then the TreeMap will consider it as duplicate, and it will not insert the keys in the Map. 

Let's discuss how we can sort the TreeMap elements on the basis of values.

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

TreeMap: Sorting a TreeMap by Values