Added new Java programs: ArmstrongInRange, LargestInArray, PalindromeNumber, and PerfectNumber

[souravCoder1]

🧩 Explanation

This pull request adds four new Java programs to the repository.
Each program demonstrates basic logic building, loops, and number theory concepts useful for beginners.

📘 Summary of Added Files

1. ArmstrongInRange.java – Displays all Armstrong numbers within a given range.
2. LargestInArray.java – Finds the largest element in a user-provided array.
3. PalindromeNumber.java – Checks whether a given number is a palindrome.
4. PerfectNumber.java – Determines whether a number is a perfect number.

🎯 Context

These programs extend the collection of beginner-friendly Java exercises in the repository and align with the style of existing examples.

🚀 Purpose

To enhance the Java section with new examples that help learners practice:

• Loops (for, while)
• Conditional statements
• Basic mathematical logic
• User input handling using Scanner