Question

为什么这段代码不能进入if语句？

public class GradeCalculator {
    public static void main(String[] args) {
        /*
         *  A 900 - 1000(90% to 100%)   B 800 - 899(80% to 89%)     
         *  C 700 - 799(70% to 79%)     D 600 - 699(60% to 69%)     
         *  F 599 and below (Below 60%)
         */

        String Name = JOptionPane.showInputDialog("Please enter your name: ");
        String pointsEarned = JOptionPane.showInputDialog("Please enter the points earned: ");
        String possiblePoints = JOptionPane.showInputDialog("Please enter the total points possible: ");

        double pe = Double.parseDouble(pointsEarned);
        double pp = Double.parseDouble(possiblePoints);

        double grade = (pe/pp)*100;
        char LetterGrade;

        if(grade>=900){
            LetterGrade = 'A';
            JOptionPane.showMessageDialog(null, Name + " your grade percentage you earned is " + grade + "%" + " and you for an " + LetterGrade, "Your Grades", JOptionPane.PLAIN_MESSAGE);
        }
    }
}

Answer 1

您计算的百分比不会超过100.因此，只要将条件更改为 if（grade> = 90）

Answer 2

你可以简单地调试并看看那里发生了什么。添加其他块并查看等级的值。

if(grade>=900){
     LetterGrade = 'A';
     // ....
}else{
     System.out.print(grade);
}

Answer 3

您的成绩变量是一个百分比，您将其比较为您计算百分比的分数。所以看起来你想要的只是使用pe而不是grade变量。

if(pe>=900){

然后仅显示

时的百分比

double percentage = (pe/pp)*100
JOptionPane.showMessageDialog(null, Name + " your grade percentage you earned is " + percentage + "%" + " and you for an " + LetterGrade, "Your Grades", JOptionPane.PLAIN_MESSAGE);

在测试时将grade变量视为百分比

 if (grade>=90) //90%

同时

变量应始终以小写字母开头，因此LetterGrade应为letterGrade

Answer 4

这就是我解决它的方法。

import javax.swing.JOptionPane;


public class GradeCalculator

{
public static void main(String[] args)


{
    boolean exitLoop = false;

    while(exitLoop == false)
    {
        String Name = JOptionPane.showInputDialog("Please enter your name: ");

        String pointsEarned = JOptionPane.showInputDialog("Please enter the points earned: ");

        String possiblePoints = JOptionPane.showInputDialog("Please enter the total points possible: ");

        double pe = Double.parseDouble(pointsEarned);
        double pp = Double.parseDouble(possiblePoints);

        double grade = (pe*100)/pp;
        double Lgrade = pe;
        char LetterGrade;

        if(Lgrade >= 900)
        {
            LetterGrade = 'A';
            JOptionPane.showMessageDialog(null, Name + " your grade percentage you earned is " + grade + "%" + " and you got an " + LetterGrade, "Your Grades", JOptionPane.PLAIN_MESSAGE);
        } else if (Lgrade <899 && Lgrade >=800)
        {
            LetterGrade = 'B';
            JOptionPane.showMessageDialog(null, Name + " your grade percentage you earned is " + grade + "%" + " and you got an " + LetterGrade, "Your Grades", JOptionPane.PLAIN_MESSAGE);
        } else if (Lgrade <799 && Lgrade >=700)
        {
            LetterGrade = 'C';
            JOptionPane.showMessageDialog(null, Name + " your grade percentage you earned is " + grade + "%" + " and you got an " + LetterGrade, "Your Grades", JOptionPane.PLAIN_MESSAGE);
        } else if (Lgrade <699 && Lgrade >=600)
        {
            LetterGrade = 'D';
            JOptionPane.showMessageDialog(null, Name + " your grade percentage you earned is " + grade + "%" + " and you got an " + LetterGrade, "Your Grades", JOptionPane.PLAIN_MESSAGE);
        } else if(Lgrade <599)
        {
            LetterGrade = 'F';
            JOptionPane.showMessageDialog(null, Name + " your grade percentage you earned is " + grade + "%" + " and you got an " + LetterGrade, "Your Grades", JOptionPane.PLAIN_MESSAGE);
        }

        int selectedOption = JOptionPane.showConfirmDialog(null, "Do you want to run the program again?", "Yes or No", JOptionPane.YES_NO_OPTION);

        if(selectedOption == JOptionPane.YES_OPTION)
        {
            exitLoop = false;
        } 
        else
        {
            exitLoop = true;
        }
    }


}

}

if语句从未执行过

4 个答案:

这就是我解决它的方法。