英文:
Index 0 out of bounds for length 0 at university_info.UniversityDriver.main(UniversityDriver.java:39)
问题
以下是您提供的代码的翻译部分：
我在尝试运行我的程序时遇到了这个错误。
有人可以帮我找出问题吗？
> 在线程“main”中的异常java.lang.ArrayIndexOutOfBoundsException：索引0超出了长度0的界限
> 位于university_info.UniversityDriver.main(UniversityDriver.java:39)
我的代码：
UniversityDriver.java
包 university_info;
导入 java.io.FileInputStream;
导入 java.io.FileNotFoundException;
导入 java.io.FileOutputStream;
导入 java.io.IOException;
导入 java.io.ObjectInputStream;
导入 java.io.ObjectOutputStream;
导入 java.util.ArrayList;
导入 java.util.Scanner;
公共类 UniversityDriver {
公共静态无效 main(String[] args) {
// TODO 自动生成的方法存根
大学 u_city = new University("hero university","好好教学");
System.out.println("欢迎来到" + u_city.universityName + "大学");
System.out.println(u_city.motto);
// 在启动时从外部文件检索数据...
ArrayList<Person> al = new ArrayList<Person>();
尝试 {
FileInputStream fis = new FileInputStream("fileName.txt");
ObjectInputStream ois = new ObjectInputStream(fis);
al = (ArrayList<Person>) ois.readObject();
ois.close();
} 捕获 (FileNotFoundException ex) {
System.out.println("文件未找到异常");
} 捕获 (IOException ex) {
ex.printStackTrace();
} 捕获 (ClassNotFoundException ex) {
}
对象[] 数组 = 新对象[al.size()];
array = al.toArray(array);
对于 (int i = 0; i <= array.length; i++) {
u_city.people[i] = (Person) array[i];
}
System.out.println("您想要做什么？");
System.out.println("输入'雇佣'以雇佣新的教职员工。 ");
System.out.println("输入'录取'以录取新的学生 ");
System.out.println("输入'查找学生'以列出有关学生的信息");
System.out.println("输入'查找教职员工'以列出有关教职员工的信息");
System.out.println("输入'列出学生'以列出所有学生的姓名。");
System.out.println("输入'列出教职员工'以列出教职员工的姓名");
System.out.println("输入'退出'以结束此程序并保存数据");
//-------------------->
扫描器 在 = 新扫描器(System.in);
布尔值 运行 = 真;
当 (运行) {
字符串 s = 在.nextLine();
如果 (s.equals("退出")) {
运行 = 假;
// 将数据保存在外部文件中
尝试 {
FileOutputStream fos = new FileOutputStream("fileName.txt");
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(u_city.people);
oos.close();
} 捕获 (IOException ex) {
ex.printStackTrace();
}
}
如果 (s.equals("雇佣")) {
u_city.hire();
}
如果 (s.equals("录取")) {
u_city.admit();
}
如果 (s.equals("查找学生")) {
System.out.println("学生的名字是什么？");
字符串 fn = 在.nextLine();
System.out.println("学生的姓氏是什么？");
字符串 ln = 在.nextLine();
学生 temp = u_city.findStudent(fn, ln);
如果 (temp == null) {
System.out.println("未找到学生");
} 否则 {
temp.Details();
}
}
如果 (s.equals("查找教职员工")) {
System.out.println("教职员工的名字是什么？");
字符串 fn = 在.nextLine();
System.out.println("教职员工的姓氏是什么？");
字符串 ln = 在.nextLine();
教职员工 temp = u_city.findFaculty(fn, ln);
如果 (temp == null) {
System.out.println("未找到教职员工");
}
}
如果 (s.equals("列出学生")) {
人[] temp = u_city.getStudents();
对于 (int i = 0; i <= temp.length; i++) {
System.out.println(temp[i].firstName + " " + temp[i].lastName);
}
}
如果 (s.equals("列出教职员工")) {
人[] temp = u_city.getFaculty();
对于 (int i = 0; i <= temp.length; i++) {
System.out.println(temp[i].firstName + " " + temp[i].lastName);
}
}
}
}
}
Faculty.java
包 university_info;
公共类 Faculty 扩展 Person {
字符串[] 课程; // 教职员工教授的课程
公共教职员工(String first, String last, int m, int d, int y, String[] course, 布尔值 bol) {
这个.课程 = 课程; //----------->
这个.firstName = first;
这个.lastName = last;
这个.monthBirth = m;
这个.dayBirth = d;
这个.yearBirth = y;
这个.student_or_faculty = bol;
}
公共无效 详情_教职员工() {
System.out.println("学生：" + 这个.firstName + " " + 这个.lastName);
System.out.println("出生日期： " + 这个.dayBirth + "/" + 这个.monthBirth + "/" + 这个.yearBirth);
System.out.println("课程： ");
对于 (int i = 0; i <= 课程.length; i++) {
System.out.println(课程[i]);
}
}
}
Person.java
包 university_info;
公共类 Person {
字符串 firstName;
字符串 lastName;
整数 monthBirth;
整数 dayBirth;
整数 yearBirth;
布尔值 student_or_faculty; // 学生为真，教职员工为假
公共人() {} //
<details>
<summary>英文:</summary>
I am getting this error when trying to run my program.
Can someone help me figure it out?
> Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 0 out of bounds for length 0
> at university_info.UniversityDriver.main(UniversityDriver.java:39)
My code:
UniversityDriver.java
package university_info;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.Scanner;
public class UniversityDriver{
public static void main(String[] args) {
// TODO Auto-generated method stub
University u_city=new University("hero university","Teach well");
System.out.println("Welcome to "+u_city.universityName+" Univercity");
System.out.println(u_city.motto);
// retrieving data from external file on startup.....
ArrayList<Person> al=new ArrayList<Person>();
try{
FileInputStream fis = new FileInputStream("fileName.txt");
ObjectInputStream ois = new ObjectInputStream(fis);
al = (ArrayList<Person>)ois.readObject();
ois.close();
}catch(FileNotFoundException ex){
System.out.println("File not found exception");
}catch(IOException ex){
ex.printStackTrace();
}catch(ClassNotFoundException ex){
}
Object[] array=new Object[al.size()];
array=al.toArray(array);
for(int i=0;i<=array.length;i++){
u_city.people[i]=(Person)array[i];
}
System.out.println("What would you like to do");
System.out.println("Enter 'hire' to hire a new faculty member. ");
System.out.println("Enter 'admit' to admit a new student ");
System.out.println("Enter 'find student' to list information about a student");
System.out.println("Enter 'find faculty' to list information about a faculty member");
System.out.println("Enter 'list students' to list the names of all students.");
System.out.println("Enter 'list faculty' to list the names of faculty members");
System.out.println("Enter 'quit' to end this program and save data");
//-------------------->
Scanner in =new Scanner(System.in);
boolean run= true;
while(run){
String s= in.nextLine();
if(s.equals("quit")){
run=false;
//save data in extenal file
try{
FileOutputStream fos = new FileOutputStream("fileName.txt");
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(u_city.people);
oos.close();
}catch(IOException ex){
ex.printStackTrace();
}
}
if(s.equals("hire")){
u_city.hire();
}
if(s.equals("admit")){
u_city.admit();
}
if(s.equals("find_student")){
System.out.println("What is the student's first name?");
String fn=in.nextLine();
System.out.println("What is the student's last name?");
String ln=in.nextLine();
Student temp=u_city.findStudent(fn, ln);
if(temp==null){
System.out.println("Student not found");
}else{
temp.Details();
}
}
if(s.equals("find_faculty")){
System.out.println("What is the faculty's first name?");
String fn=in.nextLine();
System.out.println("What is the faculty's last name?");
String ln=in.nextLine();
Faculty temp=u_city.findFaculty(fn, ln);
if(temp==null){
System.out.println("faculty not found");
}
}
if(s.equals("list_student")){
Person[] temp= u_city.getStudents();
for(int i=0;i<=temp.length;i++){
System.out.println(temp[i].firstName+" "+temp[i].lastName);
}
}
if(s.equals("list_faculty")){
Person[] temp= u_city.getFaculty();
for(int i=0;i<=temp.length;i++){
System.out.println(temp[i].firstName+" "+temp[i].lastName);
}
}
}
}
}
Faculty.java
package university_info;
public class Faculty extends Person {
String[] courses; // courses that faculty member teaches
public Faculty(String first,String last,int m,int d,int y,String[] course,boolean bol){
this.courses=course; //----------->
this.firstName=first;
this.lastName=last;
this.monthBirth=m;
this.dayBirth=d;
this.yearBirth=y;
this.student_or_faculty=bol;
}
public void Details_Faculty(){
System.out.println("Student:"+ this.firstName +" "+ this.lastName);
System.out.println("DOB: "+ this.dayBirth+"/"+this.monthBirth+"/"+this.yearBirth);
System.out.println("Courses: ");
for(int i=0;i<=courses.length;i++){
System.out.println(courses[i]);
}
}
}
Person.java
package university_info;
public class Person {
String firstName;
String lastName;
int monthBirth;
int dayBirth;
int yearBirth;
boolean student_or_faculty; // true for student and false for faculty
public Person(){} //must have a constructor
}
School.java
package university_info;
public interface School {
Student findStudent(String fn,String ln);
Faculty findFaculty(String fn,String ln);
Faculty hire();
Student admit();
Person[] getAllPersons();
String[] getAllMajors();
String[] getAllCourses();
Person[] getStudents();
Person[] getFaculty();
}
Student.java
package university_info;
public class Student extends Person {
String major;
public Student(String first,String last,int m,int d,int y,String major,boolean bol){
this.major=major;
this.firstName=first;
this.lastName=last;
this.monthBirth=m;
this.dayBirth=d;
this.yearBirth=y;
this.student_or_faculty=bol;
} // must have a constructor
public void Details(){
System.out.println("Student:"+ this.firstName +" "+ this.lastName);
System.out.println("DOB: "+ this.dayBirth+"/"+this.monthBirth+"/"+this.yearBirth);
System.out.println("Major: "+this.major);
}
}
University.java
package university_info;
import java.util.Scanner;
public class University implements School {
int MAX_SIZE= 500;
String universityName;
String motto;
Person[] people;
String[] majors;
String[] courses;
public University(String u_Name,String u_motto){
this.universityName=u_Name;
this.motto=u_motto;
people=new Person[MAX_SIZE];
majors=new String[4];
majors[0]= "Hardware Architecture";
majors[1]= "Information Analytics";
majors[2]= "Quantum Computing";
majors[3]= "Undecided";
courses=new String[12];
courses[0]="Computers";
courses[1]="Advance Physics";
courses[2]="Quantum Entanglement";
courses[3]="Parallel Programming";
courses[4]="Advance Algorithums";
courses[5]="FPGA Programming";
courses[6]="Hardware Design";
courses[7]="Embedded Systems";
courses[8]="Signal Processing";
courses[9]="Artificial Intelligence";
courses[10]="Bayesian Logic";
courses[11]="Probablity";
}
public Student findStudent(String fn, String ln) {
// TODO Auto-generated method stub
for(int i=0;i<=people.length;i++){
if(people[i].firstName.equals(fn)&& people[i].lastName.equals(ln));
return (Student)people[i];
}
return null;
}
public Faculty findFaculty(String fn, String ln) {
// TODO Auto-generated method stub
for(int i=0;i<=people.length;i++){
if(people[i].firstName.equals(fn)&& people[i].lastName.equals(ln));
return (Faculty)people[i];
}
return null;
}
public Faculty hire() {
// TODO Auto-generated method stub
Scanner in =new Scanner(System.in);
String s= in.nextLine();
System.out.println("You entered string "+s);
System.out.println("What is the person's first name?");
String f_name= in.nextLine();
System.out.println("What is the person's last name?");
String l_name= in.nextLine();
System.out.println("What is the person's month of birth?");
int m= in.nextInt();
System.out.println("What is the person's day of birth?");
int d= in.nextInt();
System.out.println("What is the person's year of birth?");
int y= in.nextInt();
String[] c=new String[20];// max 20 courses can be assigned to faculty
int i=0;
boolean condition=true;
while(condition) {
System.out.println("Assign a course to this Faculty enter 'done' if there are no other courses?");
String course= in.nextLine();
if(!course.equals("done")) {
c[i]=course;
i++;
}
condition=false;
}
boolean b=false;
Faculty temp=new Faculty(f_name,l_name,m,d,y,c,b);
return temp;
}
public Student admit() {
// TODO Auto-generated method stub
Scanner in =new Scanner(System.in);
String s= in.nextLine();
System.out.println("You entered string "+s);
System.out.println("What is the person's first name?");
String f_name= in.nextLine();
System.out.println("What is the person's last name?");
String l_name= in.nextLine();
System.out.println("What is the person's month of birth?");
int m= in.nextInt();
System.out.println("What is the person's day of birth?");
int d= in.nextInt();
System.out.println("What is the person's year of birth?");
int y= in.nextInt();
System.out.println("What is the person's major?");
String major= in.nextLine();
boolean b=true;
Student temp=new Student(f_name,l_name,m,d,y,major,b);
return temp;
}
public Person[] getAllPersons() {
// TODO Auto-generated method stub
return this.people;
}
public String[] getAllMajors() {
// TODO Auto-generated method stub
return this.majors;
}
public String[] getAllCourses() {
// TODO Auto-generated method stub
return this.courses;
}
public Person[] getStudents() {
// TODO Auto-generated method stub
Person[] temp=new Person[MAX_SIZE];
for(int i=0;i<=MAX_SIZE;i++){
if(people[i].student_or_faculty == true){
temp[i]=people[i];
}
}
return temp;
}
public Person[] getFaculty() {
// TODO Auto-generated method stub
Person[] temp=new Person[MAX_SIZE];
for(int i=0;i<=MAX_SIZE;i++){
if(people[i].student_or_faculty == false){
temp[i]=people[i];
}
}
return temp;
}
}
</details>
# 答案1
**得分**: 1
将此部分更改为：
```java
for (int i = 0; i < array.length; i++) {
u_city.people[i] = (Person) array[i];
}
将解决此问题。循环不能超过数组的大小，而且由于索引 i 从 0 开始，最大索引号可以是数组大小减一。
希望这有所帮助。
英文:
Changing this part:
for (int i = 0; i <= array.length; i++) {
u_city.people[i] = (Person) array[i];
}
to
for (int i = 0; i < array.length; i++) {
u_city.people[i] = (Person) array[i];
}
will resolve the issue. The loop cannot exceed the size of array, and since the index i starts from 0, maximum index number could be array's size minus one.
Hope this helps out.
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