创建一个程序来读取Java中的整数和字符串

Question

I am trying to create a program that will read from a .txt file that is formatted as such:

Total number of students
Name
Score1
Score2
Score3
Name
Score1
etc

My current code is this:

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.io.*;
public class Project5 {

public static void main(String[] args) throws IOException {
    Scanner in = new Scanner(System.in);
    System.out.println("Enter file name: ");
    String filename = in.nextLine();
    File filetest = new File(filename);
    Scanner imp = new Scanner(filetest);
    List<String> studentList = new ArrayList<String>();
    List<Integer> studentScores = new ArrayList<Integer>();
    String total = imp.nextLine();
    int i = 0;
    try {
        while (imp.hasNext()) {
            if (imp.hasNextInt()) {
                studentScores.add(imp.nextInt());
            } else {
                studentList.add(imp.nextLine());
            i++;
            }
        }
    } finally {
        System.out.println("Name\t\tScore1\t\tScore2\t\tScore3");
        System.out.println("-------------------------------------------------------");
        System.out.println(total);
        System.out.println(studentList.get(0) + "\t" + studentScores.subList(0, 3));
        System.out.println(studentList.get(2) + studentScores.subList(3, 6));
        System.out.println(studentList.get(4) + studentScores.subList(6, 9));
        System.out.println(studentList.get(6) + studentScores.subList(9, 12));
        imp.close();
        in.close();
    }

}
}

The format I want to display into the console is to list the name, then the three scores that student received, and to repeat it, but right now it is hard-coded just for the amount of students that are currently there, and I need it to be able to create output regardless of how many students there are.

Current output:

Total
Name [score1 score2 score3]
etc

Desired output:

Total
Name score1 score2 score3 (rather than with the [] )
etc

Any help is greatly appreciated.

Answer 1

The toString method of a List will return it in that format. If you want a different format, you can do this with a Stream :

System.out.println(studentList.get(2) + studentScores.subList(3, 6).stream().collect(Collectors.joining(" ");

Health warning: if this is for a school assignment where the use of Stream s may get you accused of plagiarism, you will need to concatenate the elements yourself the long way.

Answer 2

This is the efficient solution that uses a StringBuilder and no Lists . A StringBuilder is basically a class that helps you to build string. Pretty straightforward.

// 1024 means that the initial capacity of sb is 1024
StringBuilder sb = new StringBuilder(1024);
try {
    while (imp.hasNext()) {
        if (imp.hasNextInt()) {
            // add the scores and "tab" character to the string
            sb.append("\t").append(imp.nextInt());
        } else {
            // add the name to the string
            sb.append("\n").append(imp.nextLine());
            i++; // btw.. why are you doing this i++ ??
        }
    }
} finally {
    System.out.println("Name\t\tScore1\t\tScore2\t\tScore3");
    System.out.println("-------------------------------------------------------");
    System.out.println(total);
    System.out.println(sb.toString());
    imp.close();
    in.close();
}

If you do want to use an arraylist then I suggest iterate through the arraylist like an array and print out the scores.

Answer 3

More structural way to do this :

public class Project5 {

    static class Student {

        private String name;
        private final List<Integer> scores;
        private int total;

        public Student() {
            scores = new ArrayList<>();
            total = 0;
        }

        public void setName(String name) {
            this.name = name;
        }

        public void addScore(int score) {
            scores.add(score);
            total += score;
        }

        public String getName() {
            return name;
        }

        public List<Integer> getScores() {
            return scores;
        }

        public int getTotal() {
            return total;
        }

        @Override
        public String toString() {
            StringBuilder sb = new StringBuilder(name).append('\t').append(total);
            for (Integer score : scores) {
                sb.append('\t').append(score);
            }
            return sb.toString();
        }

    }

    public static void main(String[] args) throws IOException {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter file name: ");
        String filename = in.nextLine();
        in.close();

        File filetest = new File(filename);
        Scanner imp = new Scanner(filetest);
        int total = Integer.parseInt(imp.nextLine());

        System.out.println("Name\tTotal\tScore 1\tScore 2\tScore 3");

        for (int i = 0; i < total && imp.hasNextLine(); i++) {
            Student student = new Student();
            student.setName(imp.nextLine());
            while (imp.hasNextInt()) {
                student.addScore(imp.nextInt());
            }
            if (imp.hasNext()) {
                imp.nextLine();
            }
            System.out.println(student);
        }
        imp.close();
    }

}