有人能帮我修复这个Java代码吗？

每次我试图修复一个错误时，它都会给我一个错误接一个错误

给定以下5行5列的数组，其中包含 城市之间的距离：

请注意，城市名称不在数组中；数组包含 仅限数值项，它们给出了两个值之间的距离 由行和列表示的城市

编写语句以使用 上述里程数据

编写语句以打印以下菜单，分两部分阅读 城市编号，并打印两个城市之间的距离：

要确定城市之间的里程数，请输入里程数 以下列表中的两个城市： 1:奥尔巴尼4:纽约 2:波士顿5:费城 3:哈特福德

输入您的城市号码：

**测试用例：奥尔巴尼和纽约之间的距离&哈特福德和菲拉之间的距离

public class DistanceofCities {

private static final String keyboard = null;

public static void main(String[] args) {

    int [][] distance = {
            {0, 171, 115, 141, 240},
            {171, 0, 103, 194, 333},
            {115, 103, 0, 120, 235},
            {141, 194, 120, 0, 104},
            {240, 333, 235, 104, 0}

    };

    int mileage;
    int first = -1, second = -1;

       System.out.println("To determine the mileage between cities, enter the \n");
       System.out.println("numbers of two cities from the following list:\n");
       System.out.println("      1:  Albany           4:  NY\n");
       System.out.println("      2:  Boston           5:  Phila\n");
       System.out.println("      3:  Hartford\n\n");
       System.out.println("Enter your city numbers ==> ");
       first = keyboard.nextInt();
       second = keyboard.nextInt();
       mileage = distance[first-1][second-1];
       System.out.println("The distance between your two cities is ");
    }
}

---

看起来你没有打印最后的里程数。尝试将代码的最后一行更改为：

System.out.println("The distance between your two cities is "+mileage);

---

使用应定义键盘。使用

扫描仪
类

试试这个
导入java.util.Scanner

public class DistanceofCities {



public static void main(String[] args) {

    int [][] distance = {
            {0, 171, 115, 141, 240},
            {171, 0, 103, 194, 333},
            {115, 103, 0, 120, 235},
            {141, 194, 120, 0, 104},
            {240, 333, 235, 104, 0}

    };

    int mileage;
    int first = -1, second = -1;
       Scanner keyboard= new Scanner(System.in);
       System.out.println("To determine the mileage between cities, enter the \n");
       System.out.println("numbers of two cities from the following list:\n");
       System.out.println("      1:  Albany           4:  NY\n");
       System.out.println("      2:  Boston           5:  Phila\n");
       System.out.println("      3:  Hartford\n\n");
       System.out.println("Enter your city numbers ==> ");
       first = keyboard.nextInt();
       second = keyboard.nextInt();
       mileage = distance[first-1][second-1];
       System.out.println("The distance between your two cities is "+ mileage);
    }
}

这是固定代码；解释如下：

import java.util.Scanner;

public class DistanceOfCities {

    public static void main(String[] args) {

        Scanner keyboardReader = new Scanner(System.in);

        int[][] distance = {
                {0, 171, 115, 141, 240},
                {171, 0, 103, 194, 333},
                {115, 103, 0, 120, 235},
                {141, 194, 120, 0, 104},
                {240, 333, 235, 104, 0}

        };

        int mileage;
        int first = -1, second = -1;

        System.out.println("To determine the mileage between cities, enter the \n");
        System.out.println("numbers of two cities from the following list:\n");
        System.out.println("      1:  Albany           4:  NY\n");
        System.out.println("      2:  Boston           5:  Phila\n");
        System.out.println("      3:  Hartford\n\n");
        System.out.println("Enter your city numbers ==> ");
        first = keyboardReader.nextInt();
        second = keyboardReader.nextInt();
        mileage = distance[first - 1][second - 1];
        System.out.println("The distance between your two cities is " + mileage + ".");

    }

}

基本上，要从用户处读取键盘输入，您需要一个扫描仪对象：

// This creates the scanner:
Scanner keyboardReader = new Scanner(System.in);

您看到的错误可能是由于您试图从null对象引用调用方法nextInt（）（即指向nothing的指针）：

最后，不要忘记将里程数添加到最后得到的字符串中：

// Add mileage:
 System.out.println("The distance between your two cities is " + mileage + ".");

更改代码如下：

public static void main(String[] args) {

            int [][] distance = {
                    {0, 171, 115, 141, 240},
                    {171, 0, 103, 194, 333},
                    {115, 103, 0, 120, 235},
                    {141, 194, 120, 0, 104},
                    {240, 333, 235, 104, 0}

            };

            int mileage;
            int first = -1, second = -1;
            Scanner in = new Scanner(System.in);
               System.out.println("To determine the mileage between cities, enter the \n");
               System.out.println("numbers of two cities from the following list:\n");
               System.out.println("      1:  Albany           4:  NY\n");
               System.out.println("      2:  Boston           5:  Phila\n");
               System.out.println("      3:  Hartford\n\n");
               System.out.println("Enter your city numbers ==> ");
               first = in.nextInt();
               second = in.nextInt();
               mileage = distance[first-1][second-1];
               System.out.println("The distance between your two cities is "+mileage);
            }

请张贴错误；很难诊断一堆代码。您正在尝试的输入数字是什么。很可能，您正在尝试在两个输入数字之间输入一个enter键，但未经检查就直接转换为int。非常感谢您的帮助。最有可能的错误是编译器错误，导致String没有名为nextInt（）的方法。
public static void main(String[] args) {

            int [][] distance = {
                    {0, 171, 115, 141, 240},
                    {171, 0, 103, 194, 333},
                    {115, 103, 0, 120, 235},
                    {141, 194, 120, 0, 104},
                    {240, 333, 235, 104, 0}

            };

            int mileage;
            int first = -1, second = -1;
            Scanner in = new Scanner(System.in);
               System.out.println("To determine the mileage between cities, enter the \n");
               System.out.println("numbers of two cities from the following list:\n");
               System.out.println("      1:  Albany           4:  NY\n");
               System.out.println("      2:  Boston           5:  Phila\n");
               System.out.println("      3:  Hartford\n\n");
               System.out.println("Enter your city numbers ==> ");
               first = in.nextInt();
               second = in.nextInt();
               mileage = distance[first-1][second-1];
               System.out.println("The distance between your two cities is "+mileage);
            }