Question

我正在为类创建一个程序，该程序读取CSV文件并对文件中给出的数据执行各种数学方程式。 CSV文件位于设置中：

longitude1，latitude1，timeStamp1
longitude2，latitude2，timeStamp2
longitude3，latitude3，timeStamp3

（并继续大约100个不同的坐标）。

现在我专注于经度值 - 我很难让我的while循环执行我需要它的操作。我需要能够让程序从longitude1中减去longitude2（当我们经历循环时，lon1和lon2正在变为...最终遍历每个坐标）。

我遇到的问题是循环没有创建“重叠”（缺少更好的术语）。它在前两个坐标上执行数学运算，然后跳到下两个坐标...从而跳过其他所有操作。

[即：循环执行：lon2 - lon1和lon4-lon3但跳过lon3-lon2]

我有一种预感，我的问题出在我的while循环的开始，但老实说我不知道如何解决它。我会喜欢一些帮助。以下是我目前的代码：

import java.io.*;
import java.util.*;
public class SearchAndR {
    public static void main(String[] args) throws FileNotFoundException {
        // creates a Scanner called "keyboard" to read in the file name
        Scanner keyboard = new Scanner(System.in);
        // prompts user for file name
        System.out.println("Enter the name of the file you intend to read in");
        // Stores file name as a string so that we may read it in
        String file = keyboard.nextLine();
        // creates a new Scanner called fr(short for filereader) so we can read
        // in the file
        // then we create a File object using the constructor new with the class
        // "File"
        // this takes in our string "file" as a parameter to read it in
        // reading in our file object to the scanner
        Scanner fr = new Scanner(new File(file));
        // Creating format for hike1.csv file
        System.out.println("--- Hike Analysis ---");
        System.out.println("File: " + file);
        // Calling HW4 Class to use in the rest of the program
        HW4Util util = new HW4Util();
        // Establishing counting variable for distance for the while loop
        double totaldistance = 0;
        while (fr.hasNextLine()) {
            String line = fr.nextLine();
            String[] stamp1 = line.split(",");
            String line2 = fr.nextLine();
            String[] stamp2 = line2.split(",");
            double lon1 = Double.parseDouble(stamp1[0]);
            double lat1 = Double.parseDouble(stamp1[1]);
            String time1 = (stamp1[2]);
            double lon2 = Double.parseDouble(stamp2[0]);
            double lat2 = Double.parseDouble(stamp2[1]);
            String time2 = (stamp2[2]);
            // This is just to check to see if the overlap is occurring!
            // This should not be included in the project. 
            System.out.println("this is longitude" +lon1);
            System.out.println("this is longitude" +lon2);
            // returns the distance between two coordinates as a fraction of a
            // mile
            double dist = util.distance(lat1, lon1, lat2, lon2);
            totaldistance = totaldistance + dist;
            totaldistance = (double) (Math.round(totaldistance * 10000)) / 10000;
        }
        System.out.println("Total distance traveled: " + totaldistance + " miles");
   } // end method main
} // end class filereader

Answer 1

因为你在一次循环中读了2行。我建议做这样的事情：

String previousLine;
String[] previousStamp;
if (fr.hasNextLine())
{
   previousLine = fr.nextLine();
   previousStamp = previousLine.split(",");
}
while (fr.hasNextLine()) {
    String currentLine = fr.nextLine();
    String[] currentStamp = line.split(",");

    //do your math here
    //...

    //swap values
    previousStamp = currentStamp;
}

为什么它不按预期工作？好吧，想象一下当前处于文件开始状态的指针。使用fr.nextLine（），您正在读取当前指向的行并且指针向下。在循环的一次运行中，你会读取2个连续的行，进行数学计算，然后在下一次运行中再读取2行

虽然文件阅读器的循环问题？

1 个答案: