我需要排序方面的帮助[关闭]

Question

我想对我的文件内容进行排序。我的文件内容是学生姓名，他们的学生编号，他们的班级，他们的成绩。这些数据由“；”分隔。首先，我需要计算平均值和字母等级。我已经计算过了，但是我需要将所有内容写入另一个文件，顺序必须是最高等级到最低等级。我该怎么办？

Example of file content: Index;StdNo;Name;Surname;Average;Letter

Here is what I done by so far:

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import java.util.*;
import java.io.*;
public class project3 {

    public static void main(String[] args) {
        File file= new File("Grades.csv");
        try {
            Scanner scan = new Scanner(file);
            String[] str= new String[16];
            StringTokenizer st;
            String[] index= new String[16];
            String[] stdNo= new String[16];
            String[] name= new String[16];
            String[] surname= new String[16];
            String[] classYear= new String[16];
            String[] midterm= new String[16];
            String[] project= new String[16];
            String[] finalExam= new String[16];
        while(scan.hasNextLine()) {
            for(int i=0; i<str.length;i++) {
                str[i]=scan.nextLine();
                st=new StringTokenizer(str[i],";");
                while(st.hasMoreTokens()) {
                    index[i]=st.nextToken();
                    stdNo[i]=st.nextToken();
                    name[i]=st.nextToken();
                    surname[i]=st.nextToken();
                    classYear[i]=st.nextToken();
                    midterm[i]=st.nextToken();
                    project[i]=st.nextToken();
                    finalExam[i]=st.nextToken();
                    
                }
                
            }
        
        }
        String[] average= new String[16];
        String[] letter= new String[16];
        
        for(int i=0;i<16;i++) {
            if(i==0) {
                average[i]="Average";
                letter[i]="Letter";
                continue;
            }
            
            average[i]=averageCalculator(midterm[i],project[i],finalExam[i]);
            letter[i]=letterCalculator(averageCalculator(midterm[i],project[i],finalExam[i]));
        }
        File f= new File("Letter.csv");
        try {
            PrintWriter pw=new PrintWriter(new FileOutputStream(f));
            for(int i=0;i<16;i++)
            pw.println(index[i]+";"+stdNo[i]+";"+name[i]+";"+surname[i]+";"+average[i]+";"+letter[i]);
            pw.close();
        } catch (FileNotFoundException e) {
            System.out.println(e.getMessage());
            
        }
        File f1=new File("Ordered.csv");
            PrintWriter pw2=new PrintWriter(new FileOutputStream(f1));
        Scanner sc= new Scanner(f);
        

            
            
            
            
            
            
                
        } catch (FileNotFoundException e) {
            System.out.println(e.getMessage());
            
        }
        
            
        
    }
public static String averageCalculator(String midterm, String project, String finalExam) {
    return Double.toString((Double.parseDouble(midterm)*0.3)+(Double.parseDouble(project)*0.3)+(Double.parseDouble(finalExam)*0.4));
}
public static String letterCalculator(String average) {
    String letter="FF";
    if((Double.parseDouble(average) >=90)&&(Double.parseDouble(average) <=100)) {
        letter="AA";
    }
    else if((Double.parseDouble(average) >=85)&&(Double.parseDouble(average) <=89)) {
        letter="BA";
    }
    else if((Double.parseDouble(average) >=75)&&(Double.parseDouble(average) <=84)) {
        letter="BB";
    }
    else if((Double.parseDouble(average) >=70)&&(Double.parseDouble(average) <=74)) {
        letter="CB";
    }
    else if((Double.parseDouble(average) >=60)&&(Double.parseDouble(average) <=69)) {
        letter="CC";
    }
    else if((Double.parseDouble(average) >=55)&&(Double.parseDouble(average) <=59)) {
        letter="DC";
    }
    else if((Double.parseDouble(average) >=50)&&(Double.parseDouble(average) <=54)) {
        letter="DD";
    }
    
    return letter;
}




}

Answer 1

创建一个类来为学生数据建模

public class Student {
  private String name;
  private String surname;
  ... etc ...
}

与其将数据读入数组，不如为每行构造一个学生，并将其添加到List中。因此，读取输入文件会导致List

List<Student> students = readInputsFile(getInputFile());
calculateStuff(students);
sortByGrade(students);
writeToFile(students, getOutputFile());