java - 让 Java 能够从文本文件中读取一行并打印出来

Question

有了这个，我试图找出一种方法，以便让程序从我的“grades.txt”文本文件中读取，并在用户的输入匹配时逐行打印。 例如，如果输入的成绩是“93”，它将从文本文件中打印出“A”。

我尝试过 fileByteStream、BufferedReader、readAllLines 和 Scanner。我最终确实能够打印 "grades.txt" 但不能打印文件的实际内容。

这是我的代码:

import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
import java.util.Scanner;

public class Main {

    private static Object Paths;

    public static void main(String[] args) {
        Scanner scnr = new Scanner(System.in);
        Scanner txtscanner = new Scanner(new File("grades.txt"));


        //grades {0.0, 60.0, 70.0, 77.0, 80.0, 83.0, 87.0, 90.0, 93.0, 100.0};
        //letter grades {"F", "D", "C", "C+", "B-", "B", "B+", "A-", "A"};

        while (txtscanner.hasNextLine()) {
            System.out.println("What is your grade?");
            int grade = scnr.nextInt();

            if (grade > 100) {
                System.out.println("Invalid input");
                System.out.println("Please enter another number");
            }



            else if ((grade >= 93.00 && grade < 100)) {
                String line9 = Files.readAllLines(Paths.get("file.txt")).get(9);
                System.out.println(9);
                break;

            }
            else if (grade >= 90.0 && grade < 93) {
                System.out.print("Your grade is ");
                break;
            }
            else if (grade >= 87.0 && grade < 90) {
                System.out.print("Your grade is ");
                break;
            }
            else if (grade >= 83.0 && grade < 87) {
                System.out.print("Your grade is ");
                break;
            }
            else if (grade >= 80 && grade < 83) {
                System.out.print("Your grade is ");
                break;
            }
            else if (grade >= 77 && grade < 80) {
                System.out.print("Your grade is ");
                break;
            }
            else if (grade >= 70 && grade < 77) {
                System.out.print("Your grade is ");
                break;
            }
            else if (grade >= 60 && grade < 70) {
                System.out.print("Your grade is ");
                break;
            }
            else if (grade <= 59 && grade > 0) {
                System.out.print("Your grade is ");
                break;// write your code here
            }
        }
    }
}

Answer 1

你不需要用中断来结束 if 子句，完成的花括号会处理这个问题。您添加的中断导致它从 while 循环中弹出。由于 if .. else if .. else 的每条路径上都有一个，因此您将永远不会处理超过第一行的内容。