How do I duplicate a random unique string from a user for Java?

I want to multiply a string value to be entered from the screen as many random uniques as the number of elements in the list I have. For example, the user will enter a company name on the screen, for example NIKE. Let's say I have phone numbers on the list. How can I generate unique values ​​such as NIKE1, NIKE2, NIKE3, NIKEW, NIKEW1 as much as the number of phone numbers(list size) for Java8?