public class Student{
     private String studentNumber;
     private String studentName;
     private double studentResult;

     public Student (String aNumber,String aName){
         setStudentNumber(aNumber);
         setStudentName(aName);
         setStudentResult(0);
     }
     // The standard getter and setter method are define here.
}

在构造函数中使用setter方法的目的是什么？并且使用setStudentResult(0),我们需要另一个实例变量吗？