Difference between findBy and findOneBy in Spring data JPA

Question

All i know so far is that FindBy can return multiple results while FindOneBy will return a single result or null when we use it the following way.

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Answer 1

findOneByXX will ensure that there is only one or no value, if there are 2 values an exception will be thrown.

However findByXX doesn't make this check of uniqueness.