Best Time to Buy and Sell Stock

public class Solution {  public int maxProfit(int[] prices) {    if(prices.length == 0) return 0;    int low = prices[0];    int ans = 0;    for(int i=1; i<prices.length; i++){      if(prices[i] < low) low = prices[i];      else if(prices[i] - low > ans) ans = prices[i] - low;    }    return ans;  }}