当我尝试为我的学生添加一个新课程时，我必须检查以确保我尝试添加的课时与其他课程时间的学生不冲突，但出于某种原因，代码进入循环以检查存储在数组列表中的其他过程时间，有一个异常，当它们不应该被调用时。例如，我可以将5：00p-10：00p放入一个课程，然后放入1：00p-2：00p进行第二个课程，它会抛出异常，就像没有时会发生冲突一样。请检查注释以查看问题发生的位置。任何想法？
package myschool;
import java.util.ArrayList;
import java.util.Scanner;
public class MySchool {
private static Exception e;
public static void main(String[] args) {
ArrayList<Student> listStudent = new ArrayList<>();
ArrayList<Integer> listCourseStart = new ArrayList<>();
ArrayList<Integer> listCourseEnd = new ArrayList<>();
boolean continueLoop = true;
boolean addFirstCourse = true;
boolean addACourse = false;
Scanner userInput = new Scanner(System.in);
int option;
do{
try {
System.out.println(" What would you like to do?");
System.out.println(" 1) Add a student");
System.out.println(" 2) View students");
System.out.println(" 3) Remove a student");
System.out.println(" 4) Exit");
System.out.print("--> ");
option = userInput.nextInt();
switch( option ){
case 1:
Scanner inputs = new Scanner(System.in);
String fName, lName;
int sID;
double sGPA;
System.out.print(" First Name:");
fName = inputs.nextLine();
System.out.print(" Last Name:");
lName = inputs.nextLine();
System.out.print(" ID Number:");
sID = inputs.nextInt();
System.out.print(" GPA:");
sGPA = inputs.nextDouble();
Student newStudent = new Student(fName, lName, sID, sGPA);
listStudent.add(newStudent);
inputs.nextLine();
while (true) {
try {
System.out.println("Would you like to add a course? Y/N");
String shouldAddCourse = inputs.nextLine();
if( "N".equals(shouldAddCourse.toUpperCase()))
break;
System.out.print(" CourseName:");
String cName = inputs.nextLine();
System.out.print(" Instructor:");
String instructor = inputs.nextLine();
System.out.print(" CourseID:");
int cID = inputs.nextInt();
System.out.print(" CourseCredit:");
int cCred = inputs.nextInt();
inputs.nextLine();
System.out.print(" StartTime:");
String cStart = inputs.nextLine();
System.out.print(" AM or PM ?");
String startAMorPM = inputs.nextLine();
System.out.print(" EndTime:");
String cEnd = inputs.nextLine();
System.out.print(" AM or PM ?");
String endAMorPM = inputs.nextLine();
String cStartRemove = cStart.replace(":","");
int startInt = Integer.parseInt( cStartRemove );
String cEndRemove = cEnd.replace(":","");
int endInt = Integer.parseInt( cEndRemove );
if( "PM".equals(startAMorPM) || "pm".equals(startAMorPM) || "P".equals(startAMorPM) || "p".equals(startAMorPM) )
startInt = startInt + 1200;
if( "PM".equals(endAMorPM) || "pm".equals(endAMorPM) || "P".equals(endAMorPM) || "p".equals(endAMorPM) )
endInt = endInt + 1200;
if( addFirstCourse ){
Course newCourse = new Course( cName, instructor, cCred, cStart, cEnd, cID );
newStudent.listCourse.add(newCourse);
listCourseStart.add( startInt );
listCourseEnd.add( endInt );
addFirstCourse = false;
}else{
for( Integer r: listCourseStart ) {
if( startInt >= listCourseStart.get(r) && startInt <= listCourseEnd.get(r) /*|| endInt >= listCourseStart.get(r) && endInt <= listCourseEnd.get(r)*/ ) //the problems happens hear on the first listCourseStart.get(r)
throw e;
else
addACourse = true;
}
if( addACourse == true ){
listCourseStart.add( startInt );
listCourseEnd.add( endInt );
Course newCourse = new Course( cName, instructor, cCred, cStart, cEnd, cID );
newStudent.listCourse.add(newCourse);
addACourse = false;
}
}
} catch (Exception e) {
System.out.println("You have already added a class at that time!");
}
}
break;
case 2:
if(!listStudent.isEmpty()){
for(Student l:listStudent) {
System.out.println(l);
for(Course n:l.listCourse) {
System.out.println(n);
}
System.out.println();
}
}else
System.out.println("There are no students to view\n");
break;
case 3:
Scanner removeChoice = new Scanner(System.in);
try {
if(!listStudent.isEmpty()){
int j = 0;
System.out.println("Which student do you want to remove?");
for(Student l:listStudent) {
System.out.print(j+1 + ")");
System.out.println(l);
j++;
}
int remove = removeChoice.nextInt();
listStudent.remove( remove - 1 );
System.out.println("Student has been removed\n");
}else
System.out.println("There are no students to remove\n");
} catch (Exception e) {
System.out.println("There are no students to remove\n");
}
break;
case 4:
continueLoop = false;
break;
}
} catch (Exception e) {
System.out.println("That is not a valid option!!!");
continueLoop = false;
}
}while( continueLoop );
}
}
答案 0 :(得分：0)
你在for循环中抛出异常。
for( Integer r: listCourseStart ) {
if( startInt >= listCourseStart.get(r) && startInt <= listCourseEnd.get(r) /*|| endInt >= listCourseStart.get(r) && endInt <= listCourseEnd.get(r)*/ ) //the problems happens hear on the first listCourseStart.get(r)
throw e;// <-- This guy is the culprit, but I'm guessing you already knew that...
else
addACourse = true;
}
很难确切地说出它出错的地方（这有点难以阅读你的代码，但它应该按照你的说法行事）。
如果你正在使用IDE，你可能想要使用一些断点，并在输入变量放入列表之前检查输入变量的值，或者让它在命令行上将它们吐出来，之前将它们列入清单。
答案 1 :(得分：0)
我认为问题是你的循环
for( Integer r: listCourseStart ) { // r ist the value in listCourseStart
// you use the value 'r' as index
// you have to use for( int i = 0; i.....) or 'r' is the the right value
if( startInt >= listCourseStart.get(r) && startInt <= listCourseEnd.get(r) )
throw e;
else
addACourse = true;
}
试试这个
for( Integer r: listCourseStart ) {
if( startInt >= r && startInt <= r )
throw e;
else
addACourse = true;
}
修改
Yout在你的评论中是正确的。你的病情没有必要。您需要将开始和结束时间存储在一起。这是一个例子：
List<Integer[]> times = new ArrayList<>();
times.add(new Integer[]{900,1100});
times.add(new Integer[]{1300,1400});
for( Integer[] time : times ){
if( startInt >= time[0] && startInt <= time[1]
|| endInt >= time[0] && endInt <= time[1] ){
throw e;
}
}
一点提示：您的异常e永远不会启动 - 您将获得NullPointerException
答案 2 :(得分：0)
您在for循环中滥用列表listCourseStart。
for( Integer r: listCourseStart ) {
if( startInt >= listCourseStart.get(r) && startInt <= listCourseEnd.get(r) )
throw e;
else
addACourse = true;
}
listCourseStart是一个整数列表，用
for( Integer r: listCourseStart ) {
// ...
}
迭代列表元素。因此在第一次迭代中r将是第一个列表元素，在第二次迭代中将是第二个列表元素，依此类推。
但是在你的循环中你打电话给listCourseStart.get(r)。列表的get()方法检索给定位置的列表元素。因此，如果第一个列表元素是5，那么使用listCourseStart.get(5)，您将得到第五个列表元素。我敢肯定，这不是你想要的。
为什么不使用调试器？您可以逐步运行程序，它会显示实际的变量值，以便您可以详细了解正在进行的操作。