How do i match two subscripts in an array?

System.out.println("\nPlease enter 7 unique numbers from 1 to 80.");

            for(int i = 0; i<user.length; i++)
            {
                System.out.print("\nPlease enter number " + (i+1)+": ");
                    user[i] = sc.nextInt();
                    while(user[i]<1 || user[i] > 80)
                    {
                            System.out.println("\nPlease enter numbers from 1 to 80");
                                    user[i] = sc.nextInt();
                    }

                    for(int j = 0; j<user.length; j++)
                    {
                        if (user[i] == user[j])
                        {
                            System.out.print("\nPlease enter a unique number: ");
                                    user[i] = sc.nextInt();
                                        while(user[i]<1 || user[i] > 80)
                                        {
                                            System.out.println("\nPlease enter numbers from 1 to 80");
                                                    user[i] = sc.nextInt();
                                        }

                        }
                    }
            }

i just need to know how to tell if two subscripts in the array are the same.

the initial declaration of the array was: int[] user = new int [7]; The game I'm making is Kern btw.