错误在Java中处理InputMismatchException

Question

Im creating a lift simulation but am having trouble with the error handling. When a user inputs a letter instead of a integer it throws a InputMismatchException. How do i fix this? Here is the code below:

System.out.println("Please define... ");
        System.out.println("Number of floors:");
        Building building = new Building(in.nextInt()); 
        System.out.println("Number of lifts:");
        building.setNoOfLifts(in.nextInt());
        building.setLifts();
        System.out.println("Maximum number of people to enter building at one time:");
        building.setMaxPeople(in.nextInt());
        System.out.println("Maximum capacity of the lifts:");
        int maxLiftCapacity = in.nextInt();
        System.out.println("Simulation will now begin.");
        Queue queue = new Queue();

Answer 1

Here's some code that may help a bit. Read the integer and catch the exception in a loop. When the input is an integer, the loop exits. When an exception is thrown, the loop continues.

  Scanner sc = new Scanner(System.in);
  int i=0;
  while(true) {
      System.out.println("enter an integer:");
      try {
          int i = sc.nextInt();          
          break;
     } catch(InputMismatchException ignore){}
 }

 // i has been read successfully

Answer 2

nextInt() is only applicable if you know for certain that you will get an integral value next. (That is, the input is from a source more reliable than a user.)

What do I suggest? The broadest scope of input is a String , so take one of those. That might look something like the below.

String strFloors = in.nextLine();
strFloors = strFloors.replaceAll("[^\\d]", ""); // Strip non 1234567890 characters
intFloors = Integer.valueOf(strFloors);
Building building = new Building(intFloors);

Or if you want to fit it into just the one line, you could put it together like

Building building = new Building(Integer.valueOf(in.nextLine().replaceAll("[^\\d]", "")));

The best error handling is certainty of none arising.