Byte Bender

### Describe your change: * [x] Add an algorithm? * [ ] Fix a bug or typo in an existing algorithm? * [x] Add or change doctests? -- Note: Please...

Create SumOfOddNumbers.java

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- [x] I have read [CONTRIBUTING.md](https://github.com/TheAlgorithms/Java/blob/master/CONTRIBUTING.md). - [x] This pull request is all my own work -- I have not plagiarized it. - [x] All filenames are in PascalCase. -...

Regarding Issue #667

Feature request for a sign alter function

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A function that can alter the sign of number. Denoted by `+/-`, which can be found on many calculator apps. E.g.: **-3** will become **3** I would like to add...