How do I use strings from user input in an if-else statement that leads to picking 4 random numbers 1-56?

I've tried looking all over for a way to do this, and this is all that I've come up with so far.

import java.util.Scanner;

public class RandomPerkSelector {

public static void main(String [] args){
Scanner userInput = new Scanner(System.in);
System.out.println("What are you playing as?");

I'm a little new to this, so I may have worded it wrong, but the 2 specific roles I can choose are killer and survivor. If the user inputs "killer", I want the program to pick 4 random numbers of 1-51, and if the user inputs "survivor", I want the program to pick 4 random numbers of 1-56.