pick and not pick with DP

class Solution {
    public int rob(int[] nums) {
        int dp[] = new int[nums.length];
        Arrays.fill(dp,-1);
        return maxAmount(nums,nums.length-1, dp);
    }
    public int maxAmount(int[] nums, int idx, int dp[]){
        if(idx < 0){
            return 0;
        }
        if(dp[idx]!=-1){
            return dp[idx];
        }
        int max1 = maxAmount(nums,idx-2,dp) + nums[idx];
        int max2 = maxAmount(nums,idx-1,dp);
        return dp[idx] = Math.max(max1,max2);
    }
}