Question

I am having trouble with throwing and catching exceptions.

Here is the code for assignSeat(), assignSeat is called in a try block in another class.

void assignSeat(String passengerName, int x, int y) throws SeatOccupiedException, InvalidPassengerNameException
{
    Seat tSeat = airplane.getSeat(x,y);
    if (tSeat!=null)
    {
        if (passengerName.isEmpty() || !passengerName.matches("[a-zA-Z]+"))
        {
            throw new InvalidPassengerNameException();
        }
//excluded else if
    else if (foundPassenger(passengerName))
        {
                    airplane.seatList.get(airplane.seatNumber(passengerName)).unOccupy();   
                    tSeat.occupy();
                    for (int i = 0; i<passengers.size();i++)
                        if (passengers.get(i).getName().equals(passengerName))
                            passengers.get(i).changeSeat(tSeat.getSeatName());
        }
        else if (!tSeat.occupied)
        {
            tSeat.occupy();
            addPassenger(passengerName, tSeat.getSeatName());
        }
        else if (tSeat.occupied)
        {
            throw new SeatOccupiedException();
        }
    }

and here is the code that calls assignSeat() and is in another class (I won’t copy the whole class to make it look clearer)

if (afComp.currentAF != null)
            {
                try
                {
                    afComp.currentAF.assignSeat(nameField.getText(), x, y); //<-Problem here, "Unhandled exception type SeatOccupiedException"
                }
                catch (SeatOccupiedException exception) //<-Problem here, "Unreachable catch block, This exception is never thrown from the try statement body"
                {

                }
                catch(InvalidPassengerNameException exception) //<-No problems.
                {

                }
            }

Whats wrong with the try block? why won’t it throw the SeatOccupiedException?

Exception classes:

SeatOccupied:

package a2;

public class SeatOccupiedException extends Exception
{
    public SeatOccupiedException(){}
}

InvalidPassengerName:

package a2;

public class InvalidPassengerNameException extends Exception
{
    public InvalidPassengerNameException() {}
}

Every class I have is in package a2

imports for class that calls assignSeat

package a2;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.event.MouseEvent;
import java.awt.BorderLayout;
import javax.swing.*;
import javax.swing.event.*;

imports for class that has assignSeat

package a2;
import java.util.ArrayList;

Answer 1

Most probably, you have two SeatOccupiedException classes in two different packages, your method throws the class from one package while your code catches the other class.