//FileReadCharsInteractive.java

import java.util.Scanner;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

public class FileReadCharsInteractive
{
    /* Method prints characters in a file using read().
       Throws IOException if read() operation fails.
     */
    public static void readFileChars(FileReader fileReader) throws IOException
    {
        int charRead; // Data read from file

        charRead = 0;

        // Use file input stream
        System.out.print("Reading character values: ");
        while (charRead != -1) // -1 means end of file has been reached
        {
            charRead = fileReader.read(); // May throw IOException
            System.out.print(charRead + " ");
        }
        System.out.println();
    }

    /* Method closes a FileReader.
       Prints exception message if closing fails. */
    public static void closeFileReader(FileReader fileReader)
    {
        try
        {
            // Ensure fileReader references a valid object
            if (fileReader != null)
            {
                System.out.println("Closing file.");
                fileReader.close(); // close() may throw IOException if fails
            }
        }
        catch (IOException closeExcpt)
        {
            System.out.println("Error closing file: " + closeExcpt.getMessage());
        }
    }

    public static void main(String[] args)
    {
        Scanner scnr = new Scanner(System.in);
        FileReader fileReader = null; // File stream for reading chars
        String fileName;   // User defined file name
        boolean validFile; // Ensures file opened

        validFile = true;

        do
        {
            // Get file name from user
            System.out.print("Enter a valid file name (or 'q' to quit): ");
            fileName = scnr.next();

            if (fileName.equals("q"))
            {
                break; // Exit do-while loop
            }

            try
            {
                // Prompt user for input
                System.out.println("Opening file " + fileName + ".");
                // May throw FileNotFoundException
                fileReader = new FileReader(fileName);

                // If reached this statement, file opened successfully.
                validFile = true;

                // Read chars from file
                readFileChars(fileReader); // May throw IOException
            }
            catch (FileNotFoundException excpt)
            {
                System.out.println
                (
                    "Caught FileNotFoundException: "
                    + excpt.getMessage()
                );
                validFile = false;
            }
            catch (IOException excpt)
            {
                System.out.println
                (
                    "Caught IOException: "
                    + excpt.getMessage()
                );
            }
            finally
            {
                closeFileReader(fileReader); // Ensure file is closed!
            }
        }
        while (!validFile);
    }
}