Count Steps (1,2 or 3) with memoization

import java.io.*;
import java.util.*;

class NSteps123 {
    public static void main (String[] args) {
        int input = 3;
        int[] cache = new int[input+1];
        Arrays.fill(cache,-1);
        countSteps(cache,input);
        System.out.println(countSteps(cache, input));
    }
    public static int countSteps(int[] cache, int num) {

        if(num < 0){
            return 0;
        }
        if(num == 0 || num == 1){
            return 1;
        }
        if(num == 2){
            return 2;
        }else{
           if(cache[num] > -1){
               return cache[num];
           }else{
               cache[num] = countSteps(cache, num-1) + countSteps(cache,num-2)+ countSteps(cache,num-3);
           }
       }
       return cache[num];
    }
}