help compiling

[charlie mills]

I've written this code but it's not compiling. The error message is saying 'unreported exception java.io FileNotFoundException; must be caught or declared to be thrown.
I've only just learnt about creating your own methods and i'm struggling with it a bit, but i think what i've done is right.

  class CitiesAndTemperatures
	{

    Scanner keyboard = new Scanner(System.in);

	public int displayMenu() {
	
	 	int choice;
	  	System.out.println("1. Read in cities and temperature from a file");
	  	System.out.println("2. Display a list of cities and their temperatures");
	  	System.out.println("3. Sort by city in alphabetical order");
	  	System.out.println("4. Sort by temperature");
	  	System.out.println("5. Highest temperature");
	  	System.out.println("6. Lowest temperature");
	  	System.out.println("7. Add new data");
	  	System.out.println("8. Quit");
	
		System.out.print("\nEnter choice: ");
	  	choice = keyboard.nextInt();
	
		return choice;
	}
	public void controlMenu() {

        int choice;
        do {
            choice = displayMenu();
            
            ArrayList cities = new ArrayList();
            
            ArrayList temperatures = new ArrayList();
            
            if (choice == 1)
            {
                System.out.println("Cities and temperatures have been read from file.");
                
                //ArrayList cities = new ArrayList();
			
					Scanner citiesfile = new Scanner(new File("Cities.txt"));
				
					while (citiesfile.hasNext())
					{
						cities.add(citiesfile.nextLine());
					}
					
					//ArrayList temperatures = new ArrayList();
				
					Scanner temperaturesfile = new Scanner(new File("Temperatures.txt"));
				
					while (temperaturesfile.hasNext())
					{
						temperatures.add(temperaturesfile.nextInt());
					}
            }
            
            else if (choice == 2)
            {
            	
               System.out.println("List of cities and their temperatures:");
               
               for(int i = 0; i < cities.size(); i++)
				{
					System.out.println(cities.get(i) + "		" + temperatures.get(i));
				}
					
            }  

[Henry Wong]

The error message is saying 'unreported exception java.io FileNotFoundException; must be caught or declared to be thrown.

In Java, certain methods are defined to throw checked exception conditions. These are exceptions that occur, that you can't just ignore -- you either have to deal with them yourself (using try-catch clause) or you have to declare that they are not handled (and that your method can throw those exceptions). The file not found exception is one of those exceptions -- either you must handle it or your method must be declared to throw it.

Henry

[Pradeep Mudaliar]

Surround the block of code which instantiates and uses a File Object with a try-catch block as follows -

      
try {
        Scanner citiesfile = new Scanner(new File("Cities.txt"));
     //code using citiesfile
     } catch(FileNotFoundException e) {
	 System.out.println("The file Cities.txt was not found");
     }

As also mentioned by Henry, the other way of taking care of checked exceptions is to throw them from the method instead of handling them. So, you can have the controlMenu throw the Exception as follows -

public void controlMenu() throws FileNotFoundException {
     //your code
}

If you go ahead with this approach, methods which invoke controlMenu() would have to handle or throw the exception.