要对文件使用Scanner，必须通过File类提供文件，如下所示：

import java.io.File;
import java.io.FileNotFoundException;

public static void main(String[] args) throws FileNotFoundException {
    Scanner scan = new Scanner(new File("./members.txt"));

    /* ...Some code */
}

实际上，您是从仅包含文本“ members.txt”的流中读取的。

  

扫描仪（字符串源）

     

构造一个新的扫描仪，该扫描仪生成从指定字符串扫描的值。

因此，您正在使用构造函数htat接收字符串作为参数，而不是使用文件的字符串。看https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#Scanner(java.lang.String)

还必须使用hasNextLine函数，例如：

while (scan.hasNextLine()) {
    line = scan.nextLine();

/* some code */

}

否则您将获得异常java.util.NoSuchElementException

这是您程序的有效版本：

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;

public class Main {

    public static void main(String[] args) throws FileNotFoundException {
        Scanner scan = new Scanner(new File("./members.txt"));

        ArrayList<Student> red = new ArrayList<Student> (5);
        ArrayList<Student> blue = new ArrayList<Student> (5);
        ArrayList<Student> green = new ArrayList<Student> (5);

        // we use a map to save the index where is the captain in the array list
        HashMap<String,Integer> captains = new HashMap <String,Integer> ();

        while (scan.hasNextLine()) {
            String[] rawStudent = scan.nextLine().split(",");
            Student student = new Student(rawStudent);

            ArrayList selectedTeam = red;

            // we select dynamically the list where the student will be added
            switch (student.getTeam()) {
                case "Red": selectedTeam = red; break;
                case "Blue": selectedTeam = blue; break;
                case "Green": selectedTeam = green; break;
            }

            selectedTeam.add(student);

            if (student.isCaptain()) {
                int lastAddedIndex = selectedTeam.size() - 1;

                captains.put(student.getTeam(),lastAddedIndex);
            }
        }

        System.out.println("There are " + red.size() + " people on the red team.");
        System.out.println("There are " + blue.size() + " people on the blue team.");
        System.out.println("There are " + green.size() + " people on the green team.");

        System.out.println("The captain for the red team is: " + red.get(captains.get("Red")).getFullName());
        System.out.println("The captain for the blue team is: " + blue.get(captains.get("Blue")).getFullName());
        System.out.println("The captain for the green team is: " + green.get(captains.get("Green")).getFullName());
    }
}

class Student {
    private String name;
    private String lastName;
    private String team;
    private boolean isCaptain;

    public Student(String p1,String p2,String p3,boolean p4) {
        this.name = p1;
        this.lastName = p2;
        this.team = p3;
        this.isCaptain = p4;
    }

    public Student(String[] list) {
        this(list[0],list[1],list[2],Boolean.parseBoolean(list[3]));
    }

    public String getFullName() {
        return this.name + " " + this.lastName;
    }

    public boolean isCaptain() {
        return this.isCaptain;
    }

    public String getTeam() {
        return this.team;
    }
}

希望有帮助。

我已经制作了一个与此类似的程序，其中我正在读取不同格式的文件（例如CSV EXCEL等）并对其进行操作，因此您可以检查代码是否为行业级代码，并且可以提供更多的曝光机会，只是针对您的解决方案。

https://github.com/NahidAkhter/feeCalculator.git

简而言之，我可以在下面给出一个代码段 1）TextTransctionReader.java

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

import com.feecalculator.Constant.FILETYPE;
import com.feecalculator.Transaction;


public class TextTransctionReader extends AbstractTransactionReader implements ITransactionManager {


    @Override
    public void readTransaction(File transactionFile) {


        BufferedReader br = null;
        String line = "";
        String cvsSplitBy = ",";

        try {

            br = new BufferedReader(new FileReader(transactionFile));
            while ((line = br.readLine()) != null) {
                String[] transactionAttributes = line.split(cvsSplitBy);
                Transaction transaction = getTransaction(transactionAttributes); 
                saveTransaction(transaction);

            }        
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (br != null) {
                try {
                    br.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    }

    @Override
    public ITransactionManager readFile(FILETYPE fileType) {
        if(fileType == FILETYPE.TEXT){
            return TrasactionReader.getTrasactionReaderInstance().readTextFile();
        }
        return null;
    }


}

主要类别如下：

import java.io.File;

import com.feecalculator.Constant.FILETYPE;
import com.feecalculator.reader.ITransactionManager;
import com.feecalculator.reader.TrasactionReader;


public class MainFeeCalculator {
    public static void main(String[] args) {

        File transactionfile = new File(new File("").getAbsolutePath(),"resource/Input_java.xlsx");
        ITransactionManager tranction= TrasactionReader.getTrasactionReaderInstance().readFile(FILETYPE.EXCEL,transactionfile);     
        tranction.displayTransactionReport();   


    }
}

我希望这能解决您的问题。