我有兩個(gè) .java 文件，一個(gè)是“藍(lán)圖”，另一個(gè)只包含主要方法。我遇到的問(wèn)題是，我想打印與輸入的數(shù)字相對(duì)應(yīng)的字母。我讓它對(duì)一個(gè)“學(xué)生”對(duì)象工作正常，但是當(dāng)創(chuàng)建另一個(gè)“學(xué)生2”對(duì)象時(shí)，無(wú)論用戶輸入什么數(shù)字，每次都會(huì)打印字母“F”。請(qǐng)查看下面的代碼以更好地理解。public class StudentRecordpublic String firstName;public String lastName;public int studentID;public int courseGradeOne;//create a constructor with no args.public StudentRecord(){}//end of constructor without args.public StudentRecord(String firstName, String lastName, int studentID, int courseGradeOne){    //initializing variables.    this.firstName = firstName;    this.lastName = lastName;    this.studentID = studentID;    this.courseGradeOne = courseGradeOne;}//end of constructor with args./*Setters & Getters for all 'fields'.*/public void setFirstName(String firstName){    firstName = firstName;}//end of setter firstName.public String getFirstName(){    return firstName;}//end of getter firstName.public void setLastName(String lastName){    lastName = lastName;}//end of setter lastName.public String getLastName(){    return lastName;}//end of getter lastName.public void setStudentID(int studentID){    studentID = studentID;}//end of setter studentID.public int getStudentID(){    return studentID;}//end of getStudentID.public void setCourseGradeOne(int courseGradeOne){    courseGradeOne = courseGradeOne;}//end of setter courseGradeOne.public int getCourseGradeOne(){    return courseGradeOne;}//end of getter courseGradeOne./*Decision statements to determine "letter grade".*/public char letterReturn(){    if(courseGradeOne >= 90)        return 'A';    else        if(courseGradeOne >= 80)            return 'B';        else            if(courseGradeOne >= 70)                return 'C';            else                if(courseGradeOne >= 60)                    return 'D';                else                    if(courseGradeOne >= 50)                        return 'E';                    else                        return 'F';}//end of letterReturn.