我有三个班级Homework，其中main(...)，GradeArray有我的方法，StudentGrade有我的构造函数。
目前，这显然是错误的，我在家庭作业中：
GradeArray grade = new GradeArray（）;`
在顶部的GradeArray中我有StudentGrade[] ArrayGrades = new StudentGrade[size];但是这个方法没有给我构造和方法。我知道我不需要三节课，但我的教授想要三节课。如何声明一个包含两个类属性的数组，以便我可以从GradeArray获取方法，从StudentGrade获取构造函数？
谢谢你的时间和帮助。
这是我的所有代码
package homework1;
public class Homework1
{
public static int pubSize;
public static String pubCourseID;
public static void makeVarsPub(int maxSize, String courseID) //this is to makes the varibles public
{
pubSize = maxSize;
pubCourseID = courseID;
}
public int giveSize()
{
return pubSize;
}
public static void main(String[] args)
{
int maxSize = 100;
String courseID = "CS116";
//this is to makes the varibles public
makeVarsPub(maxSize, courseID);
StudentGrade grades = new StudentGrade();
grades.insert("Evans", 78, courseID);
grades.insert("Smith", 77, courseID);
grades.insert("Yee", 83, courseID);
grades.insert("Adams", 63, courseID);
grades.insert("Hashimoto", 91, courseID);
grades.insert("Stimson", 89, courseID);
grades.insert("Velasquez", 72, courseID);
grades.insert("Lamarque", 74, courseID);
grades.insert("Vang", 52, courseID);
grades.insert("Creswell", 88, courseID);
// print grade summary: course ID, average, how many A, B, C, D and Fs
System.out.println(grades);
String searchKey = "Stimson"; // search for item
String found = grades.find(searchKey);
if (found != null) {
System.out.print("Found ");
System.out.print(found);
}
else
System.out.println("Can't find " + searchKey);
// Find average and standard deviation
System.out.println("Grade Average: " + grades.avg());
System.out.println("Standard dev; " + grades.std());
// Show student grades sorted by name and sorted by grade
grades.reportGrades(); // sorted by name
grades.reportGradesSorted(); // sorted by grade
System.out.println("Deleting Smith, Yee, and Creswell");
grades.delete("Smith"); // delete 3 items
grades.delete("Yee");
grades.delete("Creswell");
System.out.println(grades); // display the course summary again
}//end of Main
}//end of homework1
package homework1;
class GradeArray
{
int nElems = 0; //keeping track of the number of entires in the array.
Homework1 homework1InfoCall = new Homework1(); //this is so I can get the information I need.
int size = homework1InfoCall.giveSize();
StudentGrade[] ArrayGrades = new StudentGrade[size];
public String ToString(String name, int score, String courseID)
{
String res = "Name: " + name + "\n";
res += "Score: " + score + "\n";
res += "CourseID " + courseID + "\n";
return res;
}
public String getName(int num) //returns name based on array location.
{
return ArrayGrades[num].name;
}
public double getScore(int num) //returns score based on array location.
{
return ArrayGrades[num].score;
}
public void insert(String name, double score, String courseID) //part of the insert method is going to be
//taken from lab one and modified to fit the need.
{
if(nElems == size){
System.out.println("Array is full");
System.out.println("Please delete an Item before trying to add more");
System.out.println("");
}
else{
ArrayGrades[nElems].name = name;
ArrayGrades[nElems].score = score;
ArrayGrades[nElems].courseID = courseID;
nElems++; // increment the number of elements
};
}
public void delete(String name) //code partly taken from lab1
{
int j;
for(j=0; j<nElems; j++) // look for it
if( name == ArrayGrades[j].name)
break;
if(j>nElems) // can't find it
{
System.out.println("Item not found");
}
else // found it
{
for(int k=j; k<nElems; k++) // move higher ones down
{
boolean go = true;
if ((k+2)>size)
go = false;
if(go)
ArrayGrades[k] = ArrayGrades[k+1];
}
nElems--; // decrement size
System.out.println("success");
}
}
public String find (String name){ //code partly taken from lab1
int j;
for(j=0; j<nElems; j++) // for each element,
if(ArrayGrades[j].name == name) // found item?
break; // exit loop before end
if(j == nElems) // gone to end?
return null; // yes, can't find it
else
return ArrayGrades[j].toString();
}
public double avg() //this is to get the average
{
double total = 0;
for(int j=0; j<nElems; j++)
total += ArrayGrades[j].score;
total /= nElems;
return total;
}
public double std() //this is to get the standard deviation. Information on Standard deviation derived from
//https://stackoverflow.com/questions/18390548/how-to-calculate-standard-deviation-using-java
{
double mean = 0; //this is to hold the mean
double newSum = 0;
for(int j=0; j < ArrayGrades.length; j++) //this is to get the mean.
mean =+ ArrayGrades[j].score;
for(int i=0; i < ArrayGrades.length; i++) //this is to get the new sum.
newSum =+ (ArrayGrades[i].score - mean);
mean = newSum/ArrayGrades.length; //this is to get the final answer for the mean.
return mean;
}
public StudentGrade[] reportGrades() //this is grade sorted by name
{
int in,out;
char compair; //this is for compairsons.
StudentGrade temp; //this is to hold the orginal variable.
//for the first letter cycle
for(out=1; out<ArrayGrades.length; out++)
{
temp = ArrayGrades[out];
compair= ArrayGrades[out].name.charAt(0);
in=out;
while(in>0 && ArrayGrades[in-1].name.charAt(0) > compair)
{
ArrayGrades[in] = ArrayGrades[in-1];
in--;
}
ArrayGrades[in]=temp;
}
//this is for the second run.
for(out=1; out<ArrayGrades.length; out++)
{
temp = ArrayGrades[out];
compair= ArrayGrades[out].name.charAt(1);
in=out;
while(in>0 && ArrayGrades[in-1].name.charAt(1) > compair)
{
ArrayGrades[in] = ArrayGrades[in-1];
in--;
}
ArrayGrades[in]=temp;
}
return ArrayGrades;
}
public StudentGrade[] reportGradesSorted() //this is grades sorted by grades.
//this is grabbed from lab2 and repurposed.
{
int in,out;
double temp;
for(out=1; out<ArrayGrades.length; out++)
{
temp=ArrayGrades[out].score;
in=out;
while(in>0 && ArrayGrades[in-1].score>=temp)
{
ArrayGrades[in]= ArrayGrades[in-1];
in--;
}
ArrayGrades[in].score=temp;
}
return ArrayGrades;
} //end of GradeArray
package homework1;
public class StudentGrade extends GradeArray
{
public String name;
double score;
public String courseID;
public void StudentGrade (String name, double score, String courseID) //this is the constructor
{
this.name = name;
this.score = score;
this.courseID = courseID;
}
}//end of StudentGrade class.
答案 0 :(得分：1)
首先，我觉得@Alexandr有最好的答案。和你的教授谈谈。
您的问题并未明确表达您的需求。然而，听起来对继承和类构造的基本理解会让你走上正确的道路。这3个类中的每一个都将具有该类型唯一的构造函数。这三个类中的每一个都将具有这些类型独有的方法和数据（成员）。
下面只是我汇集在一起的一个简单例子。我强烈担心我的答案实际上是你教授正在寻找的东西 - 它不是我建议的对象模型 - 只是一个例子。
public class Homework {
private String student;
public Homework(String name) {
student = name;
}
public String getStudent() {
return student;
}
}
public class StudentGrade extends Homework {
private String grade;
public StudentGrade(String grade, String name) {
super(name);
this.grade = grade;
}
public String getGrade() {
return grade;
}
}
public class HomeworkGrades {
public List<StudentGrade> getGrades() {
// this method isnt implemented but should
// be finished to return array of grades
}
}
看看是否有助于您了解有关继承和类构造的内容。
希望你能推断一下遗产（StudentGrade继承 - 在java扩展中 - 来自HomeWork）和类构造。
日Thnx 马特
答案 1 :(得分：0)
我将Homework1中的数组创建更改为StudentGrade grades = new StudentGrade();，并将extends GradeArray添加到StudentGrade类。它现在是public class StudentGrade extends GradeArray。