Question

我知道将私有变量设置为字符数据类型，但我只是好奇为什么这种技术不起作用。我已经制作了附带的模拟器。我也知道我不需要方法来做这个，但我正在尝试习惯用方法编码。

public class LetterGrade {
private String grade;
private double numGrade;
private String sign;

public LetterGrade(String grade)
{
}
public double sign()
{
    if(grade.equals("A"))
        numGrade=4.0;
    else if(grade.equals("B"))
        numGrade=3.0;
    else if(grade.equals("C"))
        numGrade=2.0;
    else if(grade.equals("D"))
        numGrade=1.0;
    else if(grade.equals("F"))
        numGrade=0.0;
    else
        System.out.println("");
    if(grade.substring(0,1).equals("-"))
        numGrade=numGrade-0.3;
    else if(grade.equals("+"))
        numGrade=numGrade+0.3;
    if(grade.equals("A+"))
        System.out.println(4.0);
    if(grade.equals("F+"))
        System.out.println("Not a valid input.");
    if(grade.equals("F-"))
        System.out.println("Not a valid input.");
   return numGrade;
}

}

    public static void main(String[]args)
{
    Scanner input=new Scanner(System.in);
    System.out.println("Enter a letter grade: ");
    String grades=input.next();
    LetterGrade grade=new LetterGrade(grades);
    System.out.print("The numeric value is " );
    System.out.println(grade.sign());
}

Answer 1

您没有在构造函数中设置字段。像这样的东西

public LetterGrade(String grade)
{
    this.grade = grade;
}

此外，我认为您希望String.startsWith(String)和String.endsWith(String)喜欢

public double sign() {
    if (grade.startsWith("A")) {
        numGrade = 4.0;
    } else if (grade.startsWith("B")) {
        numGrade = 3.0;
    } else if (grade.startsWith("C")) {
        numGrade = 2.0;
    } else if (grade.startsWith("D")) {
        numGrade = 1.0;
    } else {
        numGrade = 0.0;
    }
    if (grade.endsWith("-")) {
        numGrade -= 0.3;
    } else if (grade.endsWith("+")) {
        numGrade += 0.3;
    }
    if (grade.equals("F+")) {
        System.out.println("Not a valid input.");
    }
    if (grade.equals("F-")) {
        System.out.println("Not a valid input.");
    }
    return numGrade;
}

我正在尝试将字母等级翻译成Java中的数字等级

1 个答案: