basically this program accepts large number , find unique digits in it and also finds the largest possible number out of that unique digits.

Describe your change:

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

References

Checklist:

• [x ] I have read CONTRIBUTING.md.
• [x ] This pull request is all my own work -- I have not plagiarized.
• [ x] I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• [x ] All new Java files are placed inside an existing directory.
• [ x] All functions and variable names follow Java naming conventions.
• [ x] If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.