Java ArrayList - 错误

Question

我的代码应该从用户那里获取一系列数字，没有限制，直到用户输入负数来取消。然后它给出以下输出:1)数组中最小的数字2)数组中最大的数字3)数组中所有数字的平均值。当输入负数时，它会给我一个越界异常。

import java.util.Scanner;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class largeSmallAverage {

public static void main(String[] args) {
    // TODO Auto-generated method stub

    //Initialize array and variables
    List<Integer> userNumbers = new ArrayList<Integer>();
    double sum, average;
    sum = 0;
    average = 0;
    int i, j, counter;
    i = 0;
    j = 0;
    counter = 0;



    //Ask for input
    System.out.println("Please enter a series of numbers that you would like the average of, enter a negative number to end input");

    Scanner scan = new Scanner(System.in);

    //do while loop until a negative number is entered

    do {
        System.out.println("Please enter a number");
         i = scan.nextInt();
         userNumbers.add(i);
         counter++;

    } while ( i >= 0);

    // Sort Array

    Collections.sort(userNumbers);

    // Get Average

    for (j = 0; j < counter; j++)
        sum = sum + userNumbers.get(j);

        average = sum/counter;

    System.out.println("Minumum Number: " + userNumbers.get(0));
    System.out.println("Maximum Number: " + userNumbers.get(counter));
    System.out.println("Average: " + average);

}

}

Answer 1

问题不在于最小数部分。
问题是您在获取列表的最后一个元素时使用的计数器的索引。
列表的最后一个元素是 length-1。

System.out.println("Maximum Number: " + userNumbers.get(counter-1));