问Java中的数组索引越界错误

EN

package test1;

import java.util.Scanner;

public class Question2 {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);
        int traincars;
        int maxweight;
        int count = 0;
        int total = 0;

        maxweight = input.nextInt();
        traincars = input.nextInt();
        int[] trains = new int[traincars];

        for(int i = 0; i < traincars; i++)
        {
            trains[i] = input.nextInt();
        }

        if (total < maxweight)
        {
            for(int i = 0; i < traincars; i++)
            {
                total = trains[i] + trains[i+1] + trains[i+2] + trains[i+3];
                count++;
            }
        }else
        {
            count = count + 3;
        }
System.out.println("count");
    }
}