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

The Arrays class has a `sort()` method that is used to sort the arrays of objects and primitives. If we are sorting a primitive array, then **quicksort** is used. And if we are sorting an object array, then **merge sort** is used.

Although quicksort is faster in both cases, it is not a stable algorithm. Merge sort is a stable algorithm, so it is used in the case of sorting an object array. In the case of the primitive array, we don’t care about stability, so quicksort is used.

> Stable sorting algorithms are algorithms that maintain the relative order of equal elements. For example, we have an array [1,4,6,8,6], which we need to sort. Now after sorting this array, the result is [1,4,6,6,8]. Although there are two sixes in the array, we don’t care which six came first in the sorted array. But in the case of an object array, the relative order of elements also matters. If two objects are the same in an object array, then their relative order should be the same in the sorted array.

The sort method has two variants:

1. `sort(array)` – sorts the full array into ascending order
2. `sort(array, fromIndex, toIndex)` – sorts only the elements from *fromIndex* to *toIndex*.

Let's see how we can sort an array using the sort() method of the Arrays class.

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

Sorting an Array