Question

我有两个数据文件。数据是双精度类型。文件1由3列和几行组成，文件2由4列和几行组成。我在一个Java程序中分别从两个文件中读取数据，并且File1的第1列数据与File2的第1列数据匹配，然后出现一条消息，显示数据已匹配，否则数据不匹配。我的代码就是这样

import java.io.File;
import java.util.Scanner;

public class F1 {
public static void main(String args[])throws Exception{
    Scanner Y =new Scanner(new File("C:\\R5_M.txt"));
    Scanner X =new Scanner(new File("C:\\R5_O.txt"));
    double a=0.0,b=0.0,c,d=0.0,e=0.0,f,g,h;
    if(a==d) {
        while (X.hasNext()) {
            a = X.nextDouble();
            b = X.nextDouble();

            c = X.nextDouble();
        }


        while (Y.hasNext()) {
            d = Y.nextDouble();
            e = Y.nextDouble();

            f = Y.nextDouble();
            g = Y.nextDouble();

        }

        System.out.println("They are matched");
    }
 else{
        System.out.println("Not Matched");
    }

}

}

仅一次输出为They are matched。但是它应该写入等于行数的输出。如果我在两个数据文件中都有10行，并且匹配了6个数据，而没有匹配4个数据，则得到输出，它们匹配6次，不匹配4次。

一个明显的原因是两个循环都在该范围内结束，因此a，b，c，d，e，f，g的更改值仍保留在范围内，或者我应该说它们在每次迭代中都被覆盖如果我在while循环外调用a和d，则在这种情况下它仅返回最后一个值第十个值。那么我应该在哪里写下if语句来比较每个值？

Answer 1

您需要这样做

 public static void main(String args[])throws Exception{
        Scanner Y =new Scanner(new File("C:\\R5_M.txt"));
        Scanner X =new Scanner(new File("C:\\R5_O.txt"));
        double a=0.0,b=0.0,c,d=0.0,e=0.0,f,g,h;
        while(X.hasNext() && Y.hasNext()){
                a = X.nextDouble();
                b = X.nextDouble();

                c = X.nextDouble();

                d = Y.nextDouble();
                e = Y.nextDouble();

                f = Y.nextDouble();
                g = Y.nextDouble();

          if(a==d) {
            System.out.println("They are matched");
              }
          else{
            System.out.println("Not Matched");
           }
     }

Answer 2

一种有效的方法是使用映射存储两个文件中的每个条目，然后将两者进行比较：

import java.io.File;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) throws Exception {

        Scanner Y = new Scanner(new File("C:\\R5_M.txt"));
        Scanner X = new Scanner(new File("C:\\R5_O.txt"));
        double a = 0.0, b = 0.0, c, d = 0.0, e = 0.0, f, g, h;

        // Create a map to hold the values from each file
        HashMap<String, Double> yList = new HashMap<>();
        HashMap<String, Double> xList = new HashMap<>();

        // Read in the data from both files
        while (Y.hasNext()) {
            // This will place the values into the HashMap. The first value is whatever "key"
            // you want to use, the second is the value itself.
            yList.put("a", Y.nextDouble());
            yList.put("b", Y.nextDouble());
            yList.put("c", Y.nextDouble());
        }

        while (X.hasNext()) {
            xList.put("a", X.nextDouble());
            xList.put("b", X.nextDouble());
            xList.put("c", X.nextDouble());
        }

        // Now, you can compare values in both maps
        // The HashMap has a list called entrySet that allows you to iterate over all
        // of the entries in the list
        for (Map.Entry<String, Double> entry : yList.entrySet()) {
            // This will check if the current entry's key/value pair matches the identical
            // key/value pair in the xList map.
            if (entry.getValue() == xList.get(entry.getKey()).doubleValue()) {
                System.out.println(entry.getKey() + " matches!");
            } else {
                System.out.println(entry.getKey() + " does NOT match!");
            }
        }

    }
}

这也可以用来从每个文件读取未知数量的条目。

在Java

2 个答案: