当我尝试使用此代码执行程序时，我得到的不兼容类型inputstream无法转换为扫描程序错误。问题出在哪里？
private ArrayList<Student> readFile() throws FileNotFoundException {
readOnCampusStudent (in) ArrayList<Student> studentList = new ArrayList<Student>();
//info.add(type, id, lname, fname, resstat, prfee, credits);
String fName = "p02-students.txt";
Scanner in = new Scanner(new File(fName));
String studentType;
while (in.hasNext()) {
// studentList.add(type, id, lname, fname, resstat, prfee, credits);
if ("C".equals(in.next())) {
studentList.add(readOnCampusStudent(in));
}
studentList.add(readOnlineStudent(in));
in.nextLine();
}
in.close();
return studentList;
}
该计划有四个班级
public class Main {
public static void main(String[] args) {
new Main().run();
}
private onlineStudent readOnlineStudent(Scanner pIn) {
int id;
String lname, fname;
id = pIn.nextInt();
lname = pIn.next();
fname = pIn.next();
onlineStudent OnlineStudent = new onlineStudent(id, fname, lname) {
@Override
public void calcTuition()
{
}
};
return OnlineStudent;
}
private void calcTuition(ArrayList<Student> pStudentList) {
for (Student s : pStudentList) {
s.calcTuition();
}
}
private void run() {
ArrayList<Student> studentList = new ArrayList<Student>();
try {
studentList = readFile();
calcTuition(studentList);
Sorter.insertionSort(studentList, Sorter.SORT_ASCENDING);
writeFile(studentList);
} catch (FileNotFoundException e)
{
System.err.println("Sorry, could not open 'p02-students.txt' for reading.");
System.exit(-1);
}
}
private onCampusStudent readOnCampusStudent(Scanner pIn) {
int id = pIn.nextInt();
String lname = pIn.next();
String fname = pIn.next();
onCampusStudent OnCampusStudent = new onCampusStudent(id, fname, lname) {
@Override
public void calcTuition() {
}
};
String res = pIn.next();
double fee = pIn.nextDouble();
int credits = pIn.nextInt();
if (res.equals("R")) {
OnCampusStudent.setResidency(true);
} else {
OnCampusStudent.setResidency(false);
}
OnCampusStudent.setProgramFee(fee);
OnCampusStudent.setCredits(credits);
return OnCampusStudent;
}
private ArrayList<Student> readFile() throws FileNotFoundException {
readOnCampusStudent (in) ArrayList<Student> studentList = new ArrayList<Student>();
//info.add(type, id, lname, fname, resstat, prfee, credits);
String fName = "p02-students.txt";
Scanner in = new Scanner(new File(fName));
String studentType;
while (in.hasNext()) {
// studentList.add(type, id, lname, fname, resstat, prfee, credits);
if ("C".equals(in.next())) {
studentList.add(readOnCampusStudent(in));
}
studentList.add(readOnlineStudent(in));
in.nextLine();
}
in.close();
return studentList;
}
private void writeFile(ArrayList<Student> pStudentList) throws FileNotFoundException {
File file = new File("p02-tuition.txt");
PrintWriter out = new PrintWriter(file);
for (Student s : pStudentList) {
out.print(s.getId() + " " + s.getLName() + " " + s.getFName());
out.printf("%.2f%n", s.getTuition());
}
out.close();
}
}
public abstract class Student implements Comparable<Student> {
private int mCredits;
private String mFname;
private String mLname;
private int mId;
private double mTuition;
public Student(int pId, String pFname, String pLname) {
mId=pId;
mFname = pFname;
mLname = pLname;
}
//Implement this method in the subclass
//of student class
public abstract void calcTuition();
//Set credits of student
public void setCredits(int pCredits) {
mCredits = pCredits;
}
//Returns the credits of student
public int getCredits() {
return mCredits;
}
//Set first name
public void setFname(String pFname) {
mFname = pFname;
}
//Returns first name
public String getFirstName() {
return mFname;
}
//Set id
public void setid(int pId) {
mId = pId;
}
//Retunrns id
public int getid() {
return mId;
}
//Set last name
public void setLname(String pLname) {
mLname = pLname;
}
//Returns last name
public String getLastName() {
return mLname;
}
//Returns the tuition fee
public void setTuition(double pTuition) {
mTuition = pTuition;
}
//Returns the tuition fee
public double getTuition() {
return mTuition;
}
@Override
public int compareTo(Student pStudnet) {
if (getid() < pStudnet.getid()) {
return -1;
} else if (getid() > pStudnet.getid()) {
return 1;
} else {
return 0;
}
}
int getId() {
return mId;
}
String getLName() {
return mLname;
}
String getFName() {
return mFname;
}
void setResidency(boolean b) {
}
void setProgramFee(double fee) {
}
}
abstract class onCampusStudent extends Student
{
boolean mResident;
double mProgramFee;
onCampusStudent(int pId, String pFname, String pLname)
{
super(pId,pFname,pLname);
}
}
abstract class onlineStudent extends Student
{
boolean mResident;
double mProgramFee;
onlineStudent(int pId, String pFname, String pLname)
{
super(pId,pFname,pLname);
}
}
public class Sorter {
public static final int SORT_ASCENDING = 0;
public static final int SORT_DESCENDING = 1;
/**
* Sorts pList into ascending (pOrder = SORT_ASCENDING) or descending
* (pOrder = SORT_DESCENDING) order using the insertion sort algorithm.
*/
public static void insertionSort(ArrayList<Student> pList, int pOrder) {
for (int i = 1; i < pList.size(); ++i) {
for (int j = i; keepMoving(pList, j, pOrder); --j) {
swap(pList, j, j - 1);
}
}
}
/**
* Returns true if we need to continue moving the element at pIndex until it
* reaches its proper location.
*/
private static boolean keepMoving(ArrayList<Student> pList, int pIndex, int pOrder) {
if (pIndex < 1) {
return false;
}
Student after = pList.get(pIndex);
Student before = pList.get(pIndex - 1);
return (pOrder == SORT_ASCENDING) ? after.compareTo(before) < 0 : after.compareTo(before) > 0;
}
/**
* Swaps the elements in pList at pIndex1 and pIndex2.
*/
private static void swap(ArrayList<Student> pList, int pIndex1, int pIndex2) {
Student temp = pList.get(pIndex1);
pList.set(pIndex1, pList.get(pIndex2));
pList.set(pIndex2, temp);
}
}
public class TuitionConstants {
public static final int ONCAMP_ADD_CREDITS = 350;
public static final int MAX_CREDITS = 18;
public static final int ONCAMP_NONRES_BASE = 12200;
public static final int ONCAMP_RES_BASE = 5500;
public static final int ONLINE_CREDIT_RATE = 875;
public static final int ONLINE_TECH_FEE = 125;
}
C 8230123345450 Flintstone Fred R 0 12
C 3873472785863 Simpson Lisa N 750 18
C 4834324308675 Jetson George R 0 20
O 1384349045225 Szyslak Moe - 6
O 5627238253456 Flanders Ned T 3
答案 0 :(得分：0)
这些代码行都在你的主要类中：
import static java.lang.System.in;
Scanner in = new Scanner(new File(fName));
你有两个叫做“in”的东西。这可能会导致错误 - 它是否被导入的“in”（这是一个InputStream）或变量“in”（它是一个Scanner）感到困惑。我建议你不要导入java.lang.System .in并且只要在想要使用那个时输入System.in。然后它不会与你的变量发生冲突。
答案 1 :(得分：0)
private ArrayList<Student> readFile() throws FileNotFoundException {
String fName = "p02-students.txt";
Scanner scan = new Scanner(new File(fName));
ArrayList<Student> studentList = new ArrayList<Student>();
while (scan.hasNext()) {
String studentType = scan.next();
if (studentType.equals("C")) {
studentList.add(readOnCampusStudent(scan));
} else {
studentList.add(readOnlineStudent(scan));
}
scan.nextLine();
}
scan.close();
return studentList;
}
我没有收到您之前提到的错误，但由于您没有正确读取数据，我收到输入不匹配错误。
例如，您试图存储＆＃34; 8230123345450＆＃34;进入 int 变量。根据java标准， int 变量的值应介于2147483647和-2147483648之间。因此，我建议您使用 long 类型变量或其他String类型变量来存储它。
private onCampusStudent readOnCampusStudent(Scanner pIn) {
String id = pIn.next();
String lname = pIn.next();
String fname = pIn.next();
System.out.println(id + " " + lname + " " + fname);
}
我打印出了价值观，并且对每个学生都很好。不要忘记更改学生班级中 mid 变量的数据类型。