Here are some challenges you can work on to practice using HashMap:

1. Word Frequency Counter: Write a program that takes a string of text as input and outputs the frequency of each word in the
text. Use a HashMap to store the words and their frequency.

2. Phone Book: Write a program that allows a user to store and look up phone numbers for…Read More

Solution for Character Frequency Counter Challenge :
Topic Used to Implement this challenge : HashMap

Task : Take String as input and print unique characters as string
Topic used to Implement : HashSet