Added SubSet sum solution in Java

[deytulsi18]

Added SubSet sum solution in Java

Pull Request checklist -

• [x] This pull request fixes #issue_reference (Create an issue if not already present.)
• [x] The directory structure is of the form (directory_name) (If directory doesn't exist, create a new.)
• [x] Don't duplicate stuff.

Make sure all the above conditions are met before a PR is created.

[deytulsi18]

Please review and merge it.