added the solution for longest common substring in java

[Sahilphide]

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Description 📜

• added the dp solution of question Longest Common Substring in java

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Type of change 📝

• Code
• Documentation (Content Creation in the form of codes or tutorials)
• Notes (Handwritten notes, cheatsheets, presentations, mind-maps)
• Web Dev Projects
• Others (If you choose other, Please mention changes below)

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Programming Language

• C#
• C++
• Python
• Java
• Javascript
• Others

Domain of Contribution 📊

• Introduction
• Data Structures
• Algorithms
• Competitive Programming
• Mathematics
• Bit Magic
• Recursion
• Arrays
• Searching
• Sorting
• Matrix
• Hashing
• String
• Linked List
• Stacks
• Queue
• Deque
• Tree
• Binary Search Tree
• Heap
• Graph
• Greedy
• Backtracking
• Dynamic Programming
• Trie
• Segment Tree
• Disjoint Set
• Others

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Checklist ✅

• I follow Contributing Guidelines & Code of conduct of this project.
• I have performed a self-review of my own code or work.
• I have commented my code, particularly in hard-to-understand areas.
• My changes generates no new warnings.

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Screenshots / Gif (Optional) 📸

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