HackerRank provides some of the best quality java challenges, including more than 64+ challenges. Those challenges help you to understand from basic to advanced levels. Once you complete those challenges, you become more confident in java. Here is the solution for all those challenges. I recommend this solution only if you're stuck somewhere.

- Welcome to Java! – Hacker Rank Solution
- Java Stdin and Stdout I – Hacker Rank Solution
- Java If-Else – Hacker Rank Solution
- Java Stdin and Stdout II – Hacker Rank Solution
- Java Output Formatting – Hacker Rank Solution
- Java Loops I – Hacker Rank Solution
- Java Loops II – Hacker Rank Solution
- Java Datatypes – Hacker Rank Solution
- Java End-of-file – Hacker Rank Solution
- Java Static Initializer Block – Hacker Rank Solution
- Java Int to String – Hacker Rank Solution
- Java Date and Time – Hacker Rank Solution
- Java Currency Formatter – Hacker Rank Solution
- Java Strings Introduction – Hacker Rank Solution
- Java Substring – Hacker Rank Solution
- Java Substring Comparisons – Hacker Rank Solution
- Java String Reverse – Hacker Rank Solution
- Java Anagrams – Hacker Rank Solution
- Java String Tokens – Hacker Rank Solution
- Pattern Syntax Checker – Hacker Rank Solution
- Java Regex – Hacker Rank Solution
- Java Regex 2 – Duplicate Words – Hacker Rank Solution
- Valid Username Regular Expression – Hacker Rank Solution
- Tag Content Extractor – Hacker Rank Solution
- Java BigDecimal – Hacker Rank Solution
- Java Primality Test – Hacker Rank Solution
- Java BigInteger – Hacker Rank Solution
- Java 1D Array – Hacker Rank Solution
- Java 2D Array – Hacker Rank Solution
- Java Subarray – Hacker Rank Solution
- Java Arraylist – Hacker Rank Solution
- Java 1D Array(Part 2) – Hacker Rank Solution
- Java List – Hacker Rank Solution
- Java Map – Hacker Rank Solution
- Java Stack – Hacker Rank Solution
- Java Hashset – Hacker Rank Solution
- Java Generics – Hacker Rank Solution
- Java Comparator – Hacker Rank Solution
- Java Sort – Hacker Rank Solution
- Java Dequeue – Hacker Rank Solution
- Java BitSet – Hacker Rank Solution
- Java Priority Queue – Hacker Rank Solution
- Java Inheritance I – Hacker Rank Solution
- Java Inheritance II – Hacker Rank Solution
- Java Abstract Class – Hacker Rank Solution
- Java Interface – Hacker Rank Solution
- Java Method Overriding – Hacker Rank Solution
- Java Method Overriding 2 (Super Keyword) – Hacker Rank Solution
- Java Instanceof Keyword – Hacker Rank Solution
- Java Iterator – Hacker Rank Solution
- Java Exception Handling (Try-Catch) – Hacker Rank Solution
- Java Exception Handling – Hacker Rank Solution
- Java Varargs – Hacker Rank Solution
- Java Reflection – Attributes – Hacker Rank Solution
- Can You Access? – Hacker Rank Solution
- Prime Checker – Hacker Rank Solution
- Java Factory Pattern – Hacker Rank Solution
- Java Singleton Pattern – Hacker Rank Solution
- Java Visitor Pattern – Hacker Rank Solution
- Java Annotations – Hacker Rank Solution
- Covariant Return Types – Hacker Rank Solution
- Java Lambda Expressions – Hacker Rank Solution
- Java MD5 – Hacker Rank Solution
- Java SHA-256 – Hacker Rank Solution