Java 打印在for循环中填充的数组

我今天带着一个非常基本的任务来这里，不知怎么搞的，我真的很困惑。 我有一个数组，看起来像这样：

代码如下：

 double population[][] = {{281.0, 296.0, 325.0, 371.0, 384.5},
    {298.6, 241.2, 301.2, 342.8, 388.7},
    {362.9, 284.1, 276.8, 353.6, 395.1},
    {393.4, 344.8, 295.6, 298.3, 375.0}};
    int year[] = {2011, 2016, 2021, 2026, 2031};
    String ageGroup[] = {"15-19", "20-24", "25-29", "30-34",};
    String output = "Actual and Projected Population in thousands by Age Group (CSO 2016)";
    output += String.format("\n%10s", "");

    for (int i = 0; i < year.length; i++) {
        output += String.format("%10s", year[i]);
    }

    output += String.format("%10s", "%Change");
    double change[] = new double[ageGroup.length];
    for (int i = 0; i < population.length; i++) {
        output += String.format("\n%10s ", ageGroup[i]);
        for (int j = 0; j < population[i].length; j++) {
            output += String.format("%10.1f", population[i][j]);
        }
        change[i] = (((population[i][4] - population[i][0])/
                population[i][0]) * 100);
        output += String.format("%10.1f", change[i]);

    }     
    output += String.format("\n\nTotal (15 - 34): ");           
    System.out.println(output);

}

我也试着在这里添加它

 for (int i = 0; i < population.length; i++) {
            output += String.format("\n%10s ", ageGroup[i]);
            for (int j = 0; j < population[i].length; j++) {
                output += String.format("%10.1f", population[i][j]);
            }
            change[i] = (((population[i][4] - population[i][0])/
                    population[i][0]) * 100);
            output += String.format("%10.1f", change[i]);
            total[i] = (population[0][i] + population[1][i]+ population[2][i]+population[3][i]+population[4][i]);

        }   

for（int i=0；i

现在，我感到困惑的是，这么简单的任务怎么会让我如此困难。

双重人口[]={{281.0，296.0，325.0，371.0，384.5}，{298.6241.2，301.2，342.8，388.7}，
double population[][] = { { 281.0, 296.0, 325.0, 371.0, 384.5 }, { 298.6, 241.2, 301.2, 342.8, 388.7 },
            { 362.9, 284.1, 276.8, 353.6, 395.1 }, { 393.4, 344.8, 295.6, 298.3, 375.0 } };
    int year[] = { 2011, 2016, 2021, 2026, 2031 };
    String ageGroup[] = { "15-19", "20-24", "25-29", "30-34", };
    String output = "Actual and Projected Population in thousands by Age Group (CSO 2016)";
    output += String.format("\n%10s", "");

    for (int i = 0; i < year.length; i++) {
        output += String.format("%10s", year[i]);
    }

    output += String.format("%10s", "%Change");
    double change[] = new double[ageGroup.length];
    for (int i = 0; i < population.length; i++) {
        output += String.format("\n%10s ", ageGroup[i]);
        for (int j = 0; j < population[i].length; j++) {
            output += String.format("%10.1f", population[i][j]);
        }
        change[i] = (((population[i][4] - population[i][0]) / population[i][0]) * 100);
        output += String.format("%10.1f", change[i]);

    }
    output += String.format("\n\nTotal (15 - 34): ");

    // here i changed the code
    // this loop will print the last from (15 to 35)
    // the outer loop iterate like 2011 2016 and so one
    for (int i = 0; i < 5; i++) {
        double temp = 0;
        // the inner loop iterate from up to down and add values
        for (int j = 0; j < 4; j++) {
            temp = temp + population[j][i];
        }
        output += String.format("%10.1f", temp);
    }
    System.out.println(output);

{ 362.9, 284.1, 276.8, 353.6, 395.1 }, { 393.4, 344.8, 295.6, 298.3, 375.0 } };
国际年[]={2011、2016、2021、2026、2031}；
字符串年龄组[]={“15-19”、“20-24”、“25-29”、“30-34”、}；
字符串输出=“按年龄组划分的千人实际和预计人口（CSO 2016）”；
输出+=String.format（“\n%10s”，”）；
对于（int i=0；i

如果讲师不把面向对象的思想传授给学生，迫使学生在数组中混淆视听，而不是对领域建模，这是一种犯罪。唉

我想这里有两把钥匙。首先，将计算与表示分开。第二，认识到行是年龄组，列是年。真的应该有方法来处理这些东西，而不仅仅是在一个

main

方法中。此外，标题和一些绒毛可以在最终输出中固定

此外，与硬编码（例如，

[4]

）不同，此代码使用数组的

.length

使添加另一个年份或另一个年龄组变得更容易

//
// a 2d array, where row is for a given agent group, and column
//  is for a given year
//
static double population[][] = { { 281.0, 296.0, 325.0, 371.0, 384.5 },
        { 298.6, 241.2, 301.2, 342.8, 388.7 },
        { 362.9, 284.1, 276.8, 353.6, 395.1 },
        { 393.4, 344.8, 295.6, 298.3, 375.0 } };
static int year[] = { 2011, 2016, 2021, 2026, 2031 };
static String ageGroup[] = { "15-19", "20-24", "25-29", "30-34", };


public static void main(String[] args)
{
    //
    // hold the totals
    //
    double[] yearTot = new double[year.length]; // total by year
    double[] agTot = new double[ageGroup.length]; //total by ag
    double[] chngAG = new double[ageGroup.length]; //change

    // loop over every age group
    for (int ag = 0; ag < ageGroup.length; ++ag) {
        // get the population for the age group, which is
        // one row in the data
        double[] valsForAG = population[ag];


        // loop over every year, which a column in a given age group
        for (int yr = 0; yr < year.length; ++yr) {
            // get the specific value
            double valForAgInYear = valsForAG[yr];

            // add to the total for the year and to the age group value
            yearTot[yr] += valForAgInYear;
            agTot[ag] += valForAgInYear;

        } // for every year 

        int en = ageGroup.length;
        int st = 0;

        // after processing an age group, calculate the change
        chngAG[ag] = ( ( (valsForAG[en] - valsForAG[st]) /
                valsForAG[st]) * 100);
    } // for every age group

    //
    // do the output
    //

    // header row
    System.out.printf("%10s", "");
    for (int y = 0; y < year.length; ++y) {
        System.out.printf("\t%7d", year[y]);
    }
    System.out.printf("\t%10s%n", "%Change");

    // data
    for (int ag = 0; ag < ageGroup.length; ++ag) {
        System.out.printf("%10s", ageGroup[ag]);
        for (int yr = 0; yr < year.length; ++yr) {
            System.out.printf("\t%7.1f", population[ag][yr]);
        }
        System.out.printf("%10.1f", chngAG[ag]);
        System.out.println();
    }

    //output the totals
    System.out.println();

    System.out.printf("%10s", "Totals:");
    for (int t = 0; t < yearTot.length; ++t) {
        System.out.printf("\t%7.1f", yearTot[t]);
    }
    System.out.println();
}

总计：1335.9 1166.1 1198.6 1365.7 1543.3

publicstaticvoidmain（字符串[]args）{
双重人口[][]={{281.0,296.0,325.0,371.0,384.5}，{298.6,241.2,301.2,342.8,388.7}，{362.9,284.1,276.8,353.6,395.1}，{393.4,344.8,295.6,298.3,375.0}；
//1.步骤：查找数组中最长的
//如果阵列的长度不同，则需要此选项，例如：
/*
双种群[][]={
{281.0, 296.0, 325.0, 371.0, 384.5},
{298.6, 241.2, 301.2, 342.8, 388.7, 0},
{362.9, 284.1, 276.8, 353.6, 395.1, 1, 2},
{393.4, 344.8, 295.6, 298.3, 375.0, 0.5}
};
*/
int lengthoflongestaray=总体[0]。长度；
对于（int i=0；i长度{
LengthoFlongeStaray=总体[i]。长度；
}
}
//2.步骤：计算总和
双倍结果[]=新的双倍[LengthoflongeStaray]；
对于（int i=0；i

说明： 为了避免混淆循环和奇特的逻辑，我创建了一个数组，它将保存名为result的计算结果

步骤： 通过将这个结果数组的长度设置为population2d数组（aka.matrix）中行的最长长度，我们可以处理行长度不完全相同的情况（参见我注释掉的示例）

步骤： 然后我们只需在2D数组中循环并求和值。当我们遍历2D数组中的一行时，我们可以从正在检查的行的“j”位置获取值，并将其添加到结果数组中“j”位置的值中

干杯，

---

A.

Swing标记已删除—这个问题与Swing GUI编程有什么关系？首先，我将收集数据，然后创建输出—将数据与演示分离。第二，您是否被限制使用数组而不是实际的域对象？并且您不需要单独的for循环来创建总计。可以在当前嵌套for循环之前创建一个总计数组，并在嵌套for循环中增加该数组中已有的值。你只需要小心你使用的索引。把它写在纸上。我犯了一个错误，就是挥杆太熟练了。我已经有一段时间没有使用GUI了。我编辑了我的帖子，向你展示了我是如何在已有的循环中填充数组的。@KevinO我必须使用数组。你能解释一下你的答案吗？仅仅转储代码并没有多大帮助。请同意@pzaenger。答案转储对任何人都没有帮助。@pzaenger亲爱的，请再次检查：）感谢您为代码提供了像样的解释。非常棒的解释！非常感谢。

//
// a 2d array, where row is for a given agent group, and column
//  is for a given year
//
static double population[][] = { { 281.0, 296.0, 325.0, 371.0, 384.5 },
        { 298.6, 241.2, 301.2, 342.8, 388.7 },
        { 362.9, 284.1, 276.8, 353.6, 395.1 },
        { 393.4, 344.8, 295.6, 298.3, 375.0 } };
static int year[] = { 2011, 2016, 2021, 2026, 2031 };
static String ageGroup[] = { "15-19", "20-24", "25-29", "30-34", };


public static void main(String[] args)
{
    //
    // hold the totals
    //
    double[] yearTot = new double[year.length]; // total by year
    double[] agTot = new double[ageGroup.length]; //total by ag
    double[] chngAG = new double[ageGroup.length]; //change

    // loop over every age group
    for (int ag = 0; ag < ageGroup.length; ++ag) {
        // get the population for the age group, which is
        // one row in the data
        double[] valsForAG = population[ag];


        // loop over every year, which a column in a given age group
        for (int yr = 0; yr < year.length; ++yr) {
            // get the specific value
            double valForAgInYear = valsForAG[yr];

            // add to the total for the year and to the age group value
            yearTot[yr] += valForAgInYear;
            agTot[ag] += valForAgInYear;

        } // for every year 

        int en = ageGroup.length;
        int st = 0;

        // after processing an age group, calculate the change
        chngAG[ag] = ( ( (valsForAG[en] - valsForAG[st]) /
                valsForAG[st]) * 100);
    } // for every age group

    //
    // do the output
    //

    // header row
    System.out.printf("%10s", "");
    for (int y = 0; y < year.length; ++y) {
        System.out.printf("\t%7d", year[y]);
    }
    System.out.printf("\t%10s%n", "%Change");

    // data
    for (int ag = 0; ag < ageGroup.length; ++ag) {
        System.out.printf("%10s", ageGroup[ag]);
        for (int yr = 0; yr < year.length; ++yr) {
            System.out.printf("\t%7.1f", population[ag][yr]);
        }
        System.out.printf("%10.1f", chngAG[ag]);
        System.out.println();
    }

    //output the totals
    System.out.println();

    System.out.printf("%10s", "Totals:");
    for (int t = 0; t < yearTot.length; ++t) {
        System.out.printf("\t%7.1f", yearTot[t]);
    }
    System.out.println();
}

         2011   2016     2021    2026    2031    %Change
15-19   281.0   296.0   325.0   371.0   384.5      36.8
20-24   298.6   241.2   301.2   342.8   388.7      30.2
25-29   362.9   284.1   276.8   353.6   395.1       8.9
30-34   393.4   344.8   295.6   298.3   375.0      -4.7

public static void main(String[] args) {
    double population[][] = {{281.0, 296.0, 325.0, 371.0, 384.5}, {298.6, 241.2, 301.2, 342.8, 388.7}, {362.9, 284.1, 276.8, 353.6, 395.1}, {393.4, 344.8, 295.6, 298.3, 375.0}};

    //1. Step: Find the longest of the arrays
    //You need this if the length of the arrays is different, for example:
    /*
    double population[][] = {
     {281.0, 296.0, 325.0, 371.0, 384.5},
     {298.6, 241.2, 301.2, 342.8, 388.7, 0},
     {362.9, 284.1, 276.8, 353.6, 395.1, 1, 2},
     {393.4, 344.8, 295.6, 298.3, 375.0, 0.5}
    };
    */
    int lengthOfLongestArray = population[0].length;
    for(int i = 0; i < population.length; i++){
        if(population[i].length > lengthOfLongestArray){
            lengthOfLongestArray = population[i].length;
        }
    }

    //2. Step: calculate the sum
    double result[] = new double[lengthOfLongestArray];
    for(int i = 0; i < population.length; i++){
        for(int j = 0; j < population[i].length; j++){
            result[j] += population[i][j];
        }
    }

    System.out.println(Arrays.toString(result));
}