java - java中如何比较两个txt文件中的元素并将它们合并到一个文件中？

Question

我已经存在两个文本文件，我想从中获取相似的数据并将这些新数据合并到一个文件中。

例如:

//info1.txt
ID,Name,LastName,WorkPlace
12345,James,Jone,Us
34563,Mike,Smith,Canada
34523,Matt,jk,Uk

//info2.txt
ID,Proj1,Proj2,Proj3,Assignment,Final
34563,60,100,75,89,50
34523,70,56,75,100,70
12345,100,90,75,89,100

我能够将这两个文本文件的信息复制到一个文本文件中，但无法将每一行中的每个元素与另一个文件中的替代元素进行比较!

我的代码:

    import java.io.*; 

    public class Merge { 
    public static void main(String[] args) throws IOException { 

    //PrintWriter object for info3.txt 
    PrintWriter pw = new PrintWriter("info3.txt"); 

    //BufferedReader object for info1.txt & info2.txt
    BufferedReader br1 = new BufferedReader(new FileReader("info1.txt")); 
    BufferedReader br2 = new BufferedReader(new FileReader("info2.txt")); 

        String line1 = br1.readLine(); 
        String line2 = br2.readLine(); 

        //loop to copy each lines of the two files to info3.txt
        while (line1 != null || line2 !=null) { 
        if(line1 != null) { 
            pw.println(line1); 
            line1 = br1.readLine(); 
        }   
        if(line2 != null) { 
            pw.println(line2); 
                line2 = br2.readLine(); 
        } 
    } 
    pw.flush(); 
    br1.close(); 
    br2.close(); 
    pw.close(); 
    } 
    } 

这就是我正在寻找的结果:(注意:“P_Average”是文件“info2.txt”中三个 Projs 的平均值)。

//merged_file.txt
ID,Name,P_Average,Assignment,Final,WorkPlace
12345,James,88.3,89,100,Us
34523,Matt,67.0,100,70,Uk
34563,Mike,78.3,89,50,Canada

Answer 1

通过使用 java 8 的 Files API，

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;

public class Merge {

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

        List<String> students = Files.readAllLines(Paths.get("info1.txt"));
        List<String> grades = Files.readAllLines(Paths.get("info2.txt"));

        List<String> results = new ArrayList<>();

        results.add("ID,Name,P_Average,Assignment,Final,WorkPlace");

        // remove header lines
        students.remove(0);
        grades.remove(0);

        for(String student : students) {
            String[] s = student.split(",");
            for(String grade : grades) {
                String[] g = grade.split(",");
                if(Objects.equals(s[0], g[0])) {
                    results.add(s[0] + "," + s[1] + "," + ((Integer.parseInt(g[1]) + Integer.parseInt(g[2]) + Integer.parseInt(g[3]))/3) + "," + g[4] + "," + g[5] + "," + s[3]);
                }
            }
        }

        Files.write(Paths.get("info3.txt"), results);

    }
}

另一种简单的方法是使用数据类(Student)和数据结构(Map)

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;

public class Merge {

    static class Student {
        String ID,Name,LastName,WorkPlace,Proj1,Proj2,Proj3,Assignment,Final;

        @Override
        public String toString() {
            return ID + "," + Name + "," + ((Integer.parseInt(Proj1) + Integer.parseInt(Proj2) + Integer.parseInt(Proj3))/3) + "," + Assignment + "," + Final + "," + WorkPlace;
        }
    }

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

        // PrintWriter object for info3.txt
        PrintWriter pw = new PrintWriter("info3.txt");

        // BufferedReader object for info1.txt & info2.txt
        BufferedReader br1 = new BufferedReader(new FileReader("info1.txt"));
        BufferedReader br2 = new BufferedReader(new FileReader("info2.txt"));

        // skip header lines
        br1.readLine();
        br2.readLine();

        Map<String, Student> map = new HashMap<>();

        String line;
        while((line = br1.readLine()) != null) {
            String[] data = line.split(",");
            Student s = new Student();
            s.ID = data[0];
            s.Name = data[1];
            s.LastName = data[2];
            s.WorkPlace = data[3];
            map.put(s.ID, s);
        }


        while((line = br2.readLine()) != null) {
            String[] data = line.split(",");
            Student s = map.get(data[0]);
            s.Proj1 = data[1];
            s.Proj2 = data[2];
            s.Proj3 = data[3];
            s.Assignment = data[4];
            s.Final = data[5];
        }

        pw.println("ID,Name,P_Average,Assignment,Final,WorkPlace");

        map.values().forEach( pw::println );

        pw.flush();
        br1.close();
        br2.close();
        pw.close();
    }
}