java - 尝试使用 if block 中的变量写入 outfile.txt

Question

我正在尝试使用 if 语句内的变量写入 outfile.txt。

当我编译它时，它一直说变量尚未初始化，而实际上它们已经初始化，一个作为字符串，另一个作为字符。

import java.io.*;

import java.util.Scanner;

public class program5{
    // read string keyboard inputs
    BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
    Scanner in = new Scanner(System.in);

    public static void main(String[] args) throws IOException{
        // read string keyboard inputs
        BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
        int i, gradeA_count = 0, gradeB_count = 0, gradeC_count = 0, 
                gradeD_count = 0, gradeF_count = 0, first_grade, 
                second_grade, third_grade, fourth_grade, 
                total_of_grades;

        String remarks, course_name, semester, instructor_name, student_name;
        char grade;
        double average_grade;
        int[] array_of_int_numbers = new int[10];
        Scanner sc = new Scanner(System.in);

        // set up a outfile to write to
        Writer outfile = new BufferedWriter(new FileWriter("e:outfile.txt")); 
        // Write the class information to the outfile
        outfile.write("               CMPS 161 Program Five, Fall 2015\n\n"); 
        // separate top and next line for ease of sight
        outfile.write("               -------------------------------- \n\n");
        System.out.println("Enter the course name: ");

        course_name=input.readLine();
        System.out.println("Enter the Semester: ");
        semester=input.readLine();
        System.out.println("Enter the Instructor: ");
        instructor_name=input.readLine();
        outfile.write("Course: " +(String.format("%-8s",course_name))+ "      Semester: " +(String.format("%-10s",semester))+ "      Instructor: " +(String.format("%-12s",instructor_name))+ "\n\n");
        outfile.write("Array Item Student Name            T1 T2 T3 T4  Avg Grade Remarks\n\n");
        outfile.write("=================================================================\n\n");

        // array initialization
        for (i = 0; i < 1; i++) array_of_int_numbers[i] = 0;

        // prompt user for a value into the array
        for (i = 0; i < 1; i++){
            System.out.println("Enter a Students Name: ");
            student_name=input.readLine();
            System.out.println("Enter the first grade: ");
            first_grade=sc.nextInt();
            System.out.println("Enter the second grade: ");
            second_grade=sc.nextInt();
            System.out.println("Enter the third grade: ");
            third_grade=sc.nextInt();
            System.out.println("Enter the fourth grade: ");
            fourth_grade=sc.nextInt();
            total_of_grades = first_grade + second_grade + third_grade + fourth_grade;
            average_grade = (double) total_of_grades / 4.0;
            System.out.println("Your average grade is " +(String.format("%.1f",average_grade))+ "\n");

            if (average_grade >= 90){
                remarks = "Excellent";
                grade = 'A';
                gradeA_count++;
            }else if (average_grade >= 80){
                remarks = "Very Good";
                grade = 'B';
                gradeB_count++;
            }else if (average_grade >= 70){
                remarks = "Good";
                grade = 'C';
                gradeC_count++;
            }else if (average_grade >= 60){
                remarks = "Poor";
                grade = 'D';
                gradeD_count++;
            }else if (average_grade >= 0){
                remarks = "Fail";
                grade = 'F';
                gradeF_count++;
            }

            outfile.write("["+i+"]"+ student_name +
                                "" + first_grade +
                                "" + second_grade +
                                "" + third_grade +
                                ""+ fourth_grade +
                                "%" + average_grade +
                                "" + grade +
                                "" + remarks + "\n");
        }

        for (i = 0; i < array_of_int_numbers.length; i++){
            System.out.println("array_of_int_numbers["+(i+1)+ "] = "+array_of_int_numbers[i]);
        }

        System.out.println("Number of A's : " + gradeA_count);
        System.out.println("Number of B's : " + gradeB_count);
        System.out.println("Number of C's : " + gradeC_count);
        System.out.println("Number of D's : " + gradeD_count);
        System.out.println("Number of F's : " + gradeF_count);
        outfile.close();
    } // end program

} // end class

我是编码新手(只是我的第五个类(class))，这是我在大学的第一个学期，任何帮助将不胜感激。

我正在使用 JGrasp，因为我的教授需要它并使用 java 进行编码。

编辑:以下是抛出的异常:

program5.java:107: error: variable grade might not have been initialized
                                "" + grade +
                                     ^
program5.java:108: error: variable remarks might not have been initialized
                                "" + remarks + "\n");
                                     ^

Answer 1

在程序开始时，当您声明grade和remarks时，您并没有初始化它。您必须将这些变量设置为默认值。

例如:

String remarks = "";
char grade = '0';

现在设置什么并不重要，因为稍后会更改。

现在，如果您知道 average_grade 永远不会为负数，那么您可以用简单的 else 替换最后一个 else if 语句。这就是为什么 Java 认为变量可能未初始化，因为 average_grade 有可能变为负值。