我已经为此苦苦挣扎了一段时间。我本质上想循环并读入由num_choices. 以下代码仅执行 else 条件。
Scanner s2 = new Scanner(System.in);
for(int i=0; i < this.num_choices; i++)
{
if(s2.hasNext())
{
System.out.println("Enter choice " + (i+1) +":");
String ch = s2.next();
//this.choices.addElement(ch);
}
else
{
System.out.println("Lets end this");
}
}
`
我得到这个：Exception in thread "main" java.util.NoSuchElementException。在主类中，这是错误指向的地方
choice2 = Integer.parseInt(read_choice2.next());
这也在一个while循环内。这是代码：
public class Main
{
public static void main(String args[]) throws IOException
{
Vector<Survey> mysurveys = new Vector<Survey>();
boolean carry_on = true;
int choice = 0;
Scanner read_choice = new Scanner(System.in);
System.out.println("Let's begin the Survey/Test application!");
while(carry_on)
{
System.out.println("What would you like to do?");
System.out.println("1. Create a new Survey");
System.out.println("2. Create a new Test");
System.out.println("3. Display a Survey");
System.out.println("4. Display a Test");
System.out.println("5. Save a Survey");
System.out.println("6. Save a Test");
System.out.println("7. Load a Survey");
System.out.println("8. Load a Test");
System.out.println("9. Quit");
System.out.println();
System.out.println("Please enter a number for the operation you want to perform: ");
choice = Integer.parseInt(read_choice.next());
/*try
{
choice = Integer.parseInt(buffer.readLine());
}
catch(InputMismatchException e)
{
System.out.println("Invalid input. Please Enter again.");
System.out.println();
//read_choice.nextInt();
}*/
switch(choice)
{
case 1:
System.out.println("Please Enter a Name for your Survey");
String in = buffer.readLine();
Survey s1 = new Survey();
s1.CreateNew(in);
mysurveys.add(s1);
////
add_question(s1.type);
break;
case 2:
System.out.println("Please Enter a Name for your Test");
//String in = buffer.readLine();
Test t1 = new Test();
//t1.CreateNew(in);
mysurveys.add(t1);
break;
////
//add_question(t1.type);
case 3:
break;
// call Survey.display()
case 4:
break;
case 5:
Survey s = new Survey();
ReadWriteFiles x = new ReadWriteFiles();
x.SaveSurvey(s);
break;
case 6:
Test t = new Test();
//ReadWriteFiles x = new ReadWriteFiles();
//x.SaveSurvey(t);
break;
case 7:
carry_on = false;
break;
default:
System.out.println("Incorrect Input. Try Again");
System.out.println();
break;
}
}
read_choice.close();
}
public static void add_question(String type) throws IOException, NullPointerException
{
Questions q = null;
boolean carry_on2 = true;
int choice2 = 0;
Scanner read_choice2 = new Scanner(System.in);
//BufferedReader buffer2=new BufferedReader(new InputStreamReader(System.in));
while (carry_on2)
{
//
System.out.println("1. Add a new T/F Question");
System.out.println("2. Add a new Multiple Choice Question");
System.out.println("3. Add a new Short Answer Question");
System.out.println("4. Add a new Essay Question");
System.out.println("5. Add a new Ranking Question");
System.out.println("6. Add a new Matching Question");
System.out.println("7. If you want to stop adding more questions, and go back to the main menu.");
System.out.println("Please enter a number for the operation you want to perform: ");
choice2 = Integer.parseInt(read_choice2.next());
/*try
{
choice2 = Integer.parseInt(buffer2.readLine());
}
catch(InputMismatchException e)
{
System.out.println("Invalid input. Please Enter again.");
System.out.println();
//read_choice2.nextInt();
}*/
switch(choice2)
{
case 1:
q = new TrueFalse();
break;
case 2:
q = new MultipleChoice();
break;
case 3:
q = new ShortAnswer();
break;
case 4:
q = new Essay();
break;
case 5:
q = new Ranking();
break;
case 6:
q = new Matching();
break;
case 7:
carry_on2 = false;
break;
default:
System.out.println("Incorrect Input.");
break;
}
q.createQuestion(type);
}
}
}
我意识到有很多乱七八糟的代码，对此我深表歉意。我只是想展示整个事情，所以更容易发现问题。帮助将不胜感激。