How to make it not to repeat WORDS? [duplicate]

This question already has an answer here:

• Java generating non-repeating random numbers 6 answers

I have an application where words are randomly selected, but at least once, two words are repeated. How should I not do it again?

My code:

https://docs.google.com/document/d/1smXzY4vKsCvZnIXwOveLDzg0A1_-mvxr_Ykia9J__Hw/edit?usp=sharing

If you ask why the code is not in the problem, but in the online document, because it can not be inserted there.