Question

我有一个构造函数类：

   public class Student
{

   //declare variables
   public int studentID;
   public String courseName;
   public int courseScore;
   public char courseGrade;

   //default constructor
   public Student()
   {

      studentID = 1;
      courseName = "CIS 2085";
      courseScore = 89;

   }

//========================================

   //constructor with parameters
   public Student(int id, String course, int score)
   {

      setStud(id, course, score);

   }

//========================================

   public String toString()
   {

      return (studentID + " " + courseName + " " + courseScore);

   }

//========================================

   public void setStud(int id, String course, int score)
   {

      studentID = id;
      courseName = course;
      courseScore = score;

   }

//========================================

   public int getStudentID()
   {

      return studentID;

   }

//========================================

   public String getCourseName()
   {

      return courseName;

   }

//========================================

   public int getCourseScore()
   {

      return courseScore;

   }

//========================================

   public char getCourseGrade()
   {

      return courseGrade;

   }

//========================================

   public static char calculateGrade(int courseScore)
   {

      if (courseScore >= 94)
      courseGrade = 'A';

      else if ((courseScore >= 85) && (courseScore <= 93))
      courseGrade = 'B';

      else if ((courseScore >= 75) && (courseScore <= 84))
      courseGrade = 'C';

      else if ((courseScore >= 65) && (courseScore <= 74))
      courseGrade = 'D';

      else
      courseGrade = 'F';

      return courseGrade;

   }

//========================================

}

到目前为止，我有我的实现类，如下所示：

   import java.util.*;

public class StudentImplementation
{

   //allow 'console' to receive input from the user
   static Scanner console = new Scanner(System.in);

   //method main
   public static void main(String[] args)
   {

      //declare variables

      //object 1: first. Uses the default constructor. 
      Student first = new Student();

      //System.out.println(first);

      //object 2: second. 
      Student second = new Student(3, "Advanced JAVA Programming", 83);

      //System.out.println(second);

      //use calculateGrade method to receive grade for object 1

      char grade = Student.calculateGrade(first.getCourseScore);
      System.out.println(grade);

   }

}

所以我尝试使用我的calculateGrade方法根据我的对象courseScore输出适当的等级。

Student类与我的实现类位于一个单独的文件中。

当我运行此程序时，我收到错误：

Exception in thread "main" java.lang.NoSuchMethodError: Student.calculateGrade(I)C
    at StudentImplementation.main(StudentImplementation.java:27)

已编辑

Answer 1

将calculateGrade方法更改为：

public char calculateGrade() {
    courseScore = this.getCourseScore(); // this refers to the student from whom you called the calculaGrade() method --> first.calculateGrade()
    if (courseScore >= 94) {
        courseGrade = 'A';
    } else if ((courseScore >= 85) && (courseScore <= 93)) {
        courseGrade = 'B';
    } else if ((courseScore >= 75) && (courseScore <= 84)) {
        courseGrade = 'C';
    } else if ((courseScore >= 65) && (courseScore <= 74)) {
        courseGrade = 'D';
    } else {
        courseGrade = 'F';
    }
    return courseGrade;
}

然后只使用first.calculateGrade（）并打印结果。

Student first = new Student();
char firstStudentGrade = first.calculateGrade();
System.out.println(firstStudentGrade);

PS：方法名称不以大写字母开头;）

Answer 2

这是您的Student课程的更干净版本，可以完成您希望它执行的操作。我已经取出了不必要的变量和方法，并将其清理了一下。

我这样做的原因是因为现在，你的代码包含很多没有意义的东西（比如在方法中添加一个参数，这样你就可以在方法本身设置参数值然后返回它，在构造函数中使用setter方法。）

public class Student {
    public int studentID;
    public String courseName;
    public int courseScore;

    public Student() {
        this(1, "CIS 2085", 89);
    }

    public Student(int id, String course, int score) {
        this.studentID = id;
        this.courseName = course;
        this.courseScore = score;
    }

    @Override
    public String toString() {
        return studentID + " " + courseName + " " + courseScore;
    }

    public int getStudentID() {
        return studentID;
    }

    public String getCourseName() {
        return courseName;
    }

    public int getCourseScore() {
        return courseScore;
    }


    public char getCourseGrade() {
        if (courseScore >= 94) {
            return 'A';
        } else if (courseScore >= 85 && courseScore <= 93) {
            return 'B';
        } else if (courseScore >= 75 && courseScore <= 84) {
            return 'C';
        } else if (courseScore >= 65 && courseScore <= 74) {
            return 'D';
        }
        return 'E';
    }

}

以下是一个示例实现：

public class StudentImplementation {

    public static void main(String[] args) {
        Student first = new Student(); //default constructor
        System.out.println(first.getCourseGrade());
        Student second = new Student(3, "Advanced JAVA Programming", 83);
        System.out.println(second.getCourseGrade());
    }

}

Answer 3

怎么样

public char CalculateGrade()
   {

      if (this.courseScore >= 94)
      courseGrade = 'A';

      else if ((this.courseScore >= 85) && (this.courseScore <= 93))
      courseGrade = 'B';

      else if ((this.courseScore >= 75) && (this.courseScore <= 84))
      courseGrade = 'C';

      else if ((this.courseScore >= 65) && (this.courseScore <= 74))
      courseGrade = 'D';

      else
      courseGrade = 'F';

      g = courseGrade;

      return g;

   }

并将其命名为

System.out.println(first.CalculateGrade());

Answer 4

创建Student对象后，只需调用您的方法......

Student first = new Student();
first.CalculateGrade();

并从您不需要的g中移除CalculateGrade(char gg)参数。

Answer 5

更改语句

char grade = Student.calculateGrade(first.getCourseScore);

到

char grade = Student.calculateGrade(first.getCourseScore());

在方法调用期间您错过了()。

从单独的类中调用mutator方法

5 个答案: