如何更改二维数组中的所有值？答案

【问题标题】：How to change all values in 2d array?如何更改二维数组中的所有值？
【发布时间】：2015-03-30 23:42:04
【问题描述】：

我是 Java 编程课程的学生，我的问题涉及将 2d 数组中的所有温度从华氏温度转换为摄氏温度。该数组包含一个月中一天中每个小时的所有温度。教练之后给了我们一个打印声明，看看数组是否转换而我的没有。 getTemperature 方法只是指出数组中的特定温度，在打印语句中使用时应该已将其转换为摄氏度。我试着这样做。

public static void main (String[] args) {
    // [day][hour]
    double[][] temps = {
        {30.9, 30.9, 30.9, 33.1, 36.0, 36.0, 37.4, 39.0, 43.0, 48.2, 51.1, 55.9, 60.1, 60.1, 60.1, 60.1, 57.0, 54.0, 53.1, 55.0, 57.0, 59.0, 57.9, 57.0},
        {57.0, 59.0, 59.0, 60.1, 61.0, 63.0, 63.0, 63.0, 63.0, 62.1, 61.0, 61.0, 60.1, 59.0, 57.9, 57.0, 55.4, 52.0, 48.9, 46.0, 44.1, 42.1, 39.0, 36.0},
        {36.0, 34.0, 32.0, 30.9, 28.9, 28.0, 26.1, 30.0, 33.8, 35.1, 37.9, 41.0, 43.0, 44.6, 43.0, 43.0, 41.0, 39.0, 36.0, 34.0, 32.0, 32.0, 28.9, 28.9},
        {30.0, 28.9, 26.6, 27.0, 28.0, 28.0, 30.9, 41.0, 48.9, 51.1, 52.0, 53.1, 54.0, 55.0, 55.0, 54.0, 53.1, 51.1, 51.1, 50.0, 48.9, 50.0, 51.8, 51.8},
        {51.1, 48.9, 48.9, 46.9, 46.0, 46.0, 45.0, 45.0, 46.0, 46.0, 46.9, 48.9, 53.1, 55.0, 55.0, 54.0, 52.0, 46.9, 44.1, 41.0, 37.9, 36.0, 33.1, 32.0},
        {30.0, 28.0, 27.0, 25.0, 23.0, 21.9, 24.1, 26.1, 28.0, 30.9, 34.0, 37.0, 39.2, 42.1, 43.0, 43.0, 43.0, 39.9, 39.0, 39.0, 37.9, 37.9, 37.0, 35.1},
        {32.0, 34.0, 34.0, 33.1, 33.1, 32.0, 32.0, 33.1, 42.1, 46.9, 52.0, 55.0, 57.0, 59.0, 57.9, 57.0, 53.1, 50.0, 48.9, 48.9, 48.9, 48.0, 48.9, 48.9},
        {48.0, 48.9, 48.9, 48.2, 48.9, 50.0, 48.9, 51.1, 55.9, 60.8, 64.0, 66.9, 69.1, 69.1, 66.9, 68.0, 64.9, 60.1, 57.0, 55.9, 57.0, 55.9, 55.0, 55.9},
        {55.0, 54.0, 54.0, 53.6, 53.1, 51.1, 51.1, 51.1, 57.9, 61.0, 66.9, 69.1, 71.1, 71.1, 70.0, 66.9, 64.0, 60.1, 57.9, 55.9, 57.0, 55.0, 54.0, 52.0},
        {50.0, 52.0, 52.0, 50.0, 48.9, 46.0, 44.1, 43.0, 41.0, 41.0, 39.0, 39.0, 39.9, 39.9, 39.0, 39.9, 39.0, 37.9, 37.9, 39.0, 39.0, 39.0, 39.0, 39.2},
        {37.9, 37.9, 37.0, 36.0, 36.0, 36.0, 36.0, 36.0, 37.0, 37.0, 37.9, 39.0, 41.0, 43.0, 46.9, 48.2, 48.9, 44.1, 39.9, 37.0, 36.0, 36.0, 34.0, 33.1},
        {32.0, 32.0, 32.0, 33.8, 34.0, 33.1, 33.1, 42.1, 52.0, 57.0, 61.0, 63.0, 64.0, 64.9, 64.0, 64.0, 64.0, 55.9, 46.9, 44.1, 42.8, 39.0, 37.0, 34.0},
        {33.1, 30.9, 30.0, 28.9, 28.0, 28.0, 28.0, 28.9, 30.9, 30.9, 33.1, 36.0, 36.0, 37.0, 39.0, 39.2, 37.9, 35.1, 30.0, 30.9, 28.9, 25.0, 24.1, 24.8},
        {24.1, 23.0, 23.0, 21.9, 23.0, 21.0, 23.0, 26.1, 37.0, 43.0, 46.9, 50.0, 51.1, 51.1, 51.1, 52.0, 51.1, 48.9, 48.0, 48.9, 50.0, 51.1, 51.1, 51.1},
        {50.0, 39.0, 33.1, 30.2, 27.0, 25.0, 23.0, 23.0, 24.1, 26.1, 27.0, 28.9, 30.9, 33.1, 34.0, 34.0, 34.0, 30.9, 30.0, 28.0, 26.1, 26.1, 24.1, 23.0},
        {23.0, 23.0, 23.0, 24.1, 25.0, 24.1, 23.0, 24.1, 26.1, 27.0, 28.9, 32.0, 34.0, 33.1, 33.1, 33.1, 32.0, 33.1, 37.0, 39.0, 42.1, 44.6, 48.2, 48.2},
        {39.9, 36.0, 36.0, 60.8, 52.0, 35.1, 36.0, 33.1, 30.0, 30.0, 30.0, 32.0, 32.0, 32.0, 33.1, 32.0, 32.0, 30.9, 30.9, 30.9, 30.0, 30.0, 30.0, 28.9},
        {28.9, 27.0, 27.0, 27.0, 27.0, 28.0, 27.0, 28.9, 33.1, 36.0, 39.0, 42.1, 44.1, 46.9, 48.0, 46.9, 45.0, 43.0, 41.0, 42.1, 39.0, 37.0, 36.0, 32.0},
        {30.9, 30.0, 28.0, 26.1, 24.1, 23.0, 21.0, 21.9, 23.0, 24.1, 25.0, 26.6, 28.0, 28.9, 30.0, 28.9, 28.0, 26.1, 25.0, 21.9, 19.9, 21.0, 19.0, 19.0},
        {19.0, 18.0, 17.1, 15.8, 15.1, 14.0, 12.9, 14.0, 17.1, 19.9, 23.0, 26.1, 28.0, 30.0, 30.9, 32.0, 30.9, 28.0, 25.0, 21.9, 21.9, 21.9, 21.0, 19.9},
        {19.9, 19.9, 21.0, 19.9, 19.9, 19.9, 21.9, 27.0, 37.0, 45.0, 48.0, 50.0, 53.1, 55.9, 57.9, 57.0, 57.0, 55.0, 53.1, 54.0, 55.9, 55.0, 55.4, 55.9},
        {55.9, 55.9, 55.9, 55.4, 55.9, 55.0, 48.9, 48.0, 59.0, 61.0, 64.0, 64.9, 66.9, 66.0, 66.9, 66.0, 64.9, 63.0, 62.1, 59.0, 57.0, 57.9, 57.0, 55.9},
        {55.0, 55.9, 55.0, 55.4, 55.0, 54.0, 57.2, 55.9, 57.0, 55.9, 46.9, 46.0, 44.1, 42.8, 41.0, 39.9, 39.0, 37.9, 37.0, 37.0, 35.1, 33.1, 32.0, 30.9},
        {30.9, 30.9, 30.9, 30.0, 30.0, 28.9, 28.0, 26.1, 27.0, 28.0, 28.0, 28.0, 28.0, 28.9, 30.0, 30.0, 30.0, 30.9, 30.9, 30.0, 30.0, 30.0, 30.0, 30.0},
        {30.0, 30.0, 30.0, 30.0, 30.2, 30.0, 30.0, 30.9, 30.9, 33.8, 33.1, 34.0, 36.0, 37.9, 39.9, 39.2, 39.0, 39.0, 37.9, 37.9, 36.0, 36.0, 36.0, 35.1},
        {35.1, 36.0, 37.9, 37.0, 37.9, 39.2, 37.0, 35.1, 35.1, 36.0, 37.9, 37.4, 39.0, 39.0, 39.2, 39.0, 39.0, 37.9, 37.9, 37.0, 37.0, 37.0, 37.0, 36.0},
        {36.0, 35.1, 34.0, 34.0, 33.1, 33.8, 32.0, 32.0, 37.4, 39.9, 45.0, 46.0, 48.0, 48.9, 50.0, 51.1, 46.9, 45.0, 41.0, 37.9, 39.0, 37.0, 36.0, 37.0},
        {35.1, 33.1, 32.0, 30.9, 30.0, 30.0, 30.0, 30.0, 33.1, 37.0, 41.0, 45.0, 46.9, 48.9, 50.0, 46.9, 45.0, 43.0, 42.1, 39.9, 39.9, 39.0, 37.9, 37.9}
    };
    convertToCelsius(temps);
    System.out.println("Day 7 - Hour 5: " + getTemperature(temps, 7, 5)); // Should be 10.0 (starting at 0)
}
    public static double getTemperature (double[][] temps, int day, int hour) {
    double temp = 0;
    double temp2 = 0;
    for (int row = 0; row < temps.length; row++) {
        for (int col = 0; col < temps[row].length; col++) {
            temp = row;
            temp2 = col;
        }
    }
    return temp + temp2;
}

public static double c2f (double c) {
    double temp = (c * 9.0/5) + 32.0;
    return temp;
}

public static void convertToCelsius(double[][] temps) {
    for (int row = 0; row < temps.length; row++) {
        for (int col = 0; col < temps[row].length; col++) {
            temps[row][col] = c2f(temps[row][col]);
        }
    }
}

【问题讨论】：

getTemperature在哪里使用day和hour？
转换成功。您的整个双精度数组已正确转换。错误在于 getTemperature 方法根本没有意义。
Nvm 正如我所说，我以某种方式将数组与其他原语混合在一起。快速提示：通过打印进行调试。请记住，您的程序只会执行您告诉它执行的操作。
@pbabcdefp "getTemperature 根本没有意义" 这就是我试图向操作员提出的问题。我喜欢尝试激发思想，而不仅仅是指出问题所在。希望操作类似于“哦，对了。我为什么要把它们传进去，我应该怎么处理它们？”。

标签： java arrays 2d temperature

【解决方案1】：

我猜你误解了“第 7 天 - 第 5 小时”作为两个数字相减的含义，但恕我直言，这只是意味着在第 7 天第 5 小时获取温度。所以 getTemperature 方法应该看起来像这样

//Assumes that day and hour counting start at 0
    public static double getTemperature (double[][] temps, int day, int hour) {
        return temps[day][hour];
    }

//Assumes that day and hour counting start at 1
    public static double getTemperature (double[][] temps, int day, int hour) {
        return temps[day-1][hour-1];
    }

【讨论】：

这是错误的。它将返回错误的结果或导致ArrayIndexOutOfBoundsException。 getTemperature(temps, 1, 1) 不会返回第 1 天 - 第 1 小时，而是第 2 天 - 第 2 小时
这取决于您使用什么样的约定来计算一天。但是，是的，如果您同意，我应该添加评论 -> 相应地进行编辑。
这无关紧要，尽管x 显然是小时，y 是天。数组访问是从零开始的。如果你想要 Day1 - Hour 1 你必须return temps[0][0]

【解决方案2】：

我不确定您为什么预计第 7 天 - 第 5 小时的温度为 10。celcious 的温度为 33.1，应该转换为 91.58 华氏度。

您的代码可以正确转换温度。只是你的getTemperature (double[][] temps, int day, int hour) 没有意义。

将该方法更改为

public static double getTemperature (double[][] temps, int day, int hour){
    return temps[day-1][hour-1];
}

现在调用这个： System.out.println("Day 7 - Hour 5: " + getTemperature(temps, 7, 5)); 返回91.58

【讨论】：