Add multiple new Java DSA problems (Linked List, Arrays, and Stack)

[satyam-jaat]

I have solved a wide range of Java DSA problems and noticed that several important questions are currently missing from the repository. I’m confident that I can contribute by adding these missing problems to improve the repository’s coverage and flexibility for learners. These additions will include well-structured Java code, proper documentation, and test cases to maintain consistency with the existing standards.