如何输入GPA数字？

Question

我想要更改输入，以确保用户输入的是整数，而不是字母，并且程序能够理解输出到机器中的数字(机器将理解数字并将该数字识别为某个GPA等级)。我只知道如何输入字母和加号/减号(它们被枚举器识别为特定的分数)，但我想颠倒这个过程，让数字输入(并被识别为分数字母)。有没有办法做到这一点？

import java.util.Scanner;
        //imports scanner
        public class Part1 {
            enum LetterGrades {
              A_PLUS ("A+", 4.33),
              A      ("A" , 4   ),
              A_MINUS("A-", 3.67),
              B_PLUS ("B+", 3.33),
              B      ("B" , 3   ),
              B_MINUS("B-", 2.67),
              C_PLUS ("C+", 2.33),
              C      ("C" , 2   ),
              C_MINUS("C-", 1.67),
              D      ("D" , 1   ),
              F      ("F" , 0   ),
              FX     ("FX", 0   );



              private final String grade_;
              private final double value_;

              //CONSTRUCTOR
              private LetterGrades(String grade, double value) {
                  grade_ = grade;
                  value_ = value;
              }

              public static double getValueFromGrade(String grade) {
                  for (LetterGrades letterGrade : LetterGrades.values()) {
                      if (letterGrade.grade_.equals(grade)) {
                          return letterGrade.value_;
                      }
                  }
                  System.out.println("Invalid grade");
                  return 0.0;
              }
            }






          public static void main (String args[]){

              String grade = "";

              double credit1;
              double credit2;
              double credit3;
              double credit4;
              double gradeValue=0;
             //Creates 4 credits
              double totPtsClass1=0;
              double totPtsClass2=0;
              double totPtsClass3=0;
              double totPtsClass4=0;
              double totPts=0;
              double totalCredits= 0;
              double gpa;
              //Points in classes, GPA
              System.out.println("Welcome to the UNG GPA Calculator!");
              String message;

              Scanner scan = new Scanner(System.in);
              System.out.println("Enter your first name: ");
              message = scan.nextLine();
              System.out.println("Enter your last name: ");
              message = scan.nextLine();
              System.out.println("Enter your major: ");
              message = scan.nextLine();
              System.out.println("Enter the class number of your first class: ");
              message = scan.nextLine();

              Scanner console = new Scanner (System.in);


              System.out.println("Please enter the number of credits of the class 1 (A number)");
              credit1 = console.nextDouble();
              System.out.println("Now you will enter the grade from the chart: A = 4.00, A- = 3.67, B+ = 3.33, B = 3.00, B- = 2.67, C+ = 2.33, C = 2.00, C- = 1.67, D+ = 1.33, D = 1.00, F = 0.00. Please enter your grades for the class 1(Capital letters such as A,B+, C-)");
              grade = console.next();


              gradeValue = LetterGrades.getValueFromGrade(grade);
              totPtsClass1 = gradeValue * credit1;

              System.out.println("Enter the class number of your second class: ");
              message = scan.nextLine();
              System.out.println("Please enter the number of credits of the class 2 (A number)");
              credit2 = console.nextDouble();
              System.out.println("Please enter your grades for the class 2 (Capital letters such as A,B+, C-)");
              grade = console.next();


              gradeValue = LetterGrades.getValueFromGrade(grade);
              totPtsClass2 = gradeValue * credit1;


              System.out.println("Please enter the number of credits of the class 3 (A number)");
              credit3 = console.nextDouble();
              System.out.println("Please enter your grades for the class 3 (Capital letters such as A,B+, C-)");
              grade = console.next();


              gradeValue = LetterGrades.getValueFromGrade(grade);
              totPtsClass3 = gradeValue * credit1;


              System.out.println("Please enter the number of credits of the class 4 (A number)");
              credit4 = console.nextDouble();
              System.out.println("Please enter your grades for the class 4 (Capital letters such as A,B+, C-)");
              grade = console.next();

              gradeValue = LetterGrades.getValueFromGrade(grade);
              totPtsClass4 = gradeValue * credit1;


              totPts= totPtsClass1 + totPtsClass2 + totPtsClass3 + totPtsClass4;
              totalCredits = credit1 + credit2 + credit3 + credit4;
              gpa= totPts / totalCredits;

              System.out.printf("Your GPA is: %.2f\n", + gpa);
         }
    }

我需要确保用户可以从枚举器列表中输入浮点数(输入的小数对应于某些GPA)如何将用户输入分配给字符串变量(程序读取它并将其分配给正确命名的变量)？

Answer 1

您可以将如下内容添加到LetterGrades枚举中：

public static LetterGrades fromValue(double value) {
    Optional<LetterGrades> result =
            Arrays.stream(LetterGrades.values())
                    .filter(grade -> Math.abs(grade.value_ - value) < 0.01)
                    .findFirst();

    if (!result.isPresent()) {
        System.out.println("Invalid grade value");
    }

    return result.orElse(FX);
}

Answer 2

以下是一种可能的解决方案：

• 任何4.33以上的等级: A+ (4.33)
• 4.32到4.0: A (4.0)
• 3.99到3.67: A- (3.67)
• ...
• 0.99 to 0: F (0)
• any negative: NULL

<代码>F213

LetterGrade.java

public enum LetterGrade {

    A_PLUS ("A+", 4.33),
    A      ("A" , 4   ),
    A_MINUS("A-", 3.67),
    B_PLUS ("B+", 3.33),
    B      ("B" , 3   ),
    B_MINUS("B-", 2.67),
    C_PLUS ("C+", 2.33),
    C      ("C" , 2   ),
    C_MINUS("C-", 1.67),
    D      ("D" , 1   ),
    F      ("F" , 0   ),
    FX     ("FX", 0   );

    private final String grade;

    private final double value;

    public String getGrade() {
        return grade;
    }

    public double getValue() {
        return value;
    }

    private LetterGrade(String grade, double value) {
        this.grade = grade;
        this.value = value;
    }

    public static LetterGrade getLetterGrade(String grade) {
        for (LetterGrade letterGrade : LetterGrade.values()) {
            if (letterGrade.grade.equals(grade)) {
                return letterGrade;
            }
        }
        return null;
    }

    public static LetterGrade getLetterGrade(double value) {
        for (LetterGrade letterGrade : LetterGrade.values()) {
            if (letterGrade.value <= value) {
                return letterGrade;
            }
        }
        return null;
    }

}