Java文件处理

Question

这是我的代码：

public class Homework{
/**
 * This is a data mining program surveying various countries' Human Development
 * Index rank (1), which is a composite statistic of life expectancy, education, and income indices
 * used to rank countries in terms of human development. This code will also examine
 * these countries' research and development expenditure (2) (measured with respect to % of GDP),
 * their number of researchers (3), the percentage of graduates who are in science and
 * engineering (4), number of patents granted (to both residents and non-residents) (5),
 * the percentage of population which owns a computer (6) and the percentage of population
 * which uses the internet (7). The above is also the chronological order for my use of columns.
 * The data used ranges from 2002-2011.
 *
 * I decided to focus on the first 150 ranked countries (as they provide
 * the most data per column) while excluding the rest of the columns
 * (royalty and license fees,electrification rate and note,
 * percentage of population which has a fixed broadband internet and telephone)
 * as these columns provided either less or redundant information.
 * As a side note, I also manually cut out the countries' "(republic of)" or "(federal state of)"
 * in the Data4.csv file to facilitate searching for countries' data.
 *
 * https://data.undp.org/dataset/Table-12-Innovation-and-technology/jixu-gnyy
 *
 * @author mbizzzle
 * @throws FileNotFoundException
 *
 */

    public static void main(String[] args) throws FileNotFoundException {
        System.out.println("Welcome to the innovation and tech data mining table");
        Scanner sc = new Scanner(System.in);
        Scanner input = new Scanner(new File("Data4.csv"));
        String data = "";

        while (input.hasNext()){
            data += input.nextLine();
            data += ";";

        }
        String[] rows = data.split(";");
        String[][] dataL = new String[rows.length][];
        int i = 0;
        for (String row : rows){
            dataL[i++] = row.split(",");

        }
        System.out.println("Please enter the name of the country you would like to examine");
        String country = sc.next();

        for (int j = 0; j<rows.length; j++){
            if (country.toLowerCase().equals(dataL[j][1].toLowerCase())){
                System.out.println("\n \n \n");
                System.out.println("DATA COVERING AVERAGES BETWEEN 2002-2011 FOR "+ country.toUpperCase()+"\n");
                System.out.println("        ---------------------------------------------        \n");
                System.out.printf("HDI is ranked number %s out of "+dataL.length+" countries \n", dataL[j][0]);
                System.out.printf("Percent of GDP in Research and Development expenditure: %s  \n", dataL[j][2]);
                System.out.printf("Number of researchers involved %s \n", dataL[j][3]);
                System.out.printf("Percentage of graduates in Science and engineering : %s \n", dataL[j][4]);
                System.out.printf("Number of patents granted to residents and nonresidents : %s \n", dataL[j][5]);
                System.out.printf("Percentage of population using personal computers : %s \n", dataL[j][6]);
                System.out.printf("Percentage of internet users : %s \n", dataL[j][7]);

            }
        }
    }
}

现在一切正常，除了：

1. 当我输入一个名字是两个字母的国家（例如：南非）时，程序将终止运行并且不给我任何数据。 我已经尝试手动设置 "South Africa".toLowercase.equals(dataL[122][1]) 来检查是否是我的数组有问题，（其中 dataL[122][1] 是多维数组的坐标对于南非）在一个布尔表达式中，这给了我 true 所以我不完全确定这里发生了什么。

2. 有谁知道我如何重新排序行，以便根据列进行排序（假设我想要使用互联网最多的国家/地区的顺序，这是我的最后一列）。

Answer 1

阅读[java.util.Scanner][1]的文档。

Scanner 使用分隔符模式将其输入分解为标记，默认情况下与空格匹配。

即如果您输入South Africa ，方法Scanner.next将返回South ，因为那里有空格。

另请注意，您正在做的是一个简单的数据库，而不是数据挖掘。 没有进行复杂的统计分析，但您只是在实施SELECT * FROM file.csv WHERE Column1 = ? 手动。