Learn about collections in Java such as LinkedLists, HashSet, HashMap and more.

Java for Programmers

Collections 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.

Java Collections

## Operations on HashMap

### Checking if a key is present in the HashMap
We can use the `containsKey(Object key)` method to check if a given key is present in the **HashMap**. This method returns `true` if the key is present and returns `false` if the key is not present. Similarly, we have a `containsValue(Object value)` method that returns true if one or more keys are mapped to this value.

# Operations on HashMap

## Checking if a key is present in the HashMap
We can use the `containsKey(Object key)` method to check if a given key is present in the **HashMap**. This method returns `true` if the key is present and returns `false` if the key is not present. Similarly, we have a `containsValue(Object value)` method that returns true if one or more keys are mapped to this value.

Introduction

ArrayList

LinkedList

CopyOnWriteArrayList

HashSet

TreeSet

HashMap

TreeMap

LinkedHashMap

Additional Map Implmentations

Arrays

Collections class

HashMap: A Few More Operations

Operations on HashMap

Checking if a key is present in the HashMap