IO.java

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class IO
{
    private static BufferedReader kb =
            new BufferedReader(new InputStreamReader(System.in));

    private static BufferedReader fio = null;

    public static boolean openFile(String filename){

        try{
            fio = new BufferedReader(new FileReader(filename));
            return true;
        }catch (IOException e){ return false;}
    }

    public static String readLine(){
        if (fio == null)
            return null;

        try{
            return fio.readLine();
        }catch(IOException e){ return null;}
    }

    public static String readString()
    {
        while (true) {
            try {
                return kb.readLine();
            } catch (IOException e) {
                // should never happen
            }
        }
    }

    public static int readInt()
    {
        while (true) {
            try {
                String s = kb.readLine();
                return Integer.parseInt(s);
            } catch (NumberFormatException e) {
                System.out.print("That is not an integer.  Enter again: ");
            } catch (IOException e) {
                // should never happen
            }
        }
    }

    public static double readDouble()
    {
        while (true) {
            try {
                String s = kb.readLine();
                return Double.parseDouble(s);
            } catch (NumberFormatException e) {
                System.out.print("That is not a number.  Enter again: ");
            } catch (IOException e) {
                // should never happen
            }
        }
    }

    public static char readChar()
    {
        String s = null;

        try {
            s = kb.readLine();
        } catch (IOException e) {
            // should never happen
        }

        while (s.length() != 1) {
            System.out.print("That is not a single character.  Enter again: ");
            try {
                s = kb.readLine();
            } catch (IOException e) {
                // should never happen
            }
        }

        return s.charAt(0);
    }

    public static boolean readBoolean()
    {
        String s = null;

        while (true) {
            try {
                s = kb.readLine();
            } catch (IOException e) {
                // should never happen
            }

            if (s.equalsIgnoreCase("yes") ||
                    s.equalsIgnoreCase("y") ||
                    s.equalsIgnoreCase("true") ||
                    s.equalsIgnoreCase("t")) {
                return true;
            } else if (s.equalsIgnoreCase("no") ||
                    s.equalsIgnoreCase("n") ||
                    s.equalsIgnoreCase("false") ||
                    s.equalsIgnoreCase("f")) {
                return false;
            } else {
                System.out.print("Enter \"yes\" or \"no\": ");
            }
        }
    }

    public static void outputStringAnswer(String s)
    {
        if (s != null) {
            System.out.println("RESULT: \"" + s + "\"");
        } else {
            System.out.println("RESULT: null");
        }
    }

    public static void outputIntAnswer(int i)
    {
        System.out.println("RESULT: " + i);
    }

    public static void outputDoubleAnswer(double d)
    {
        System.out.println("RESULT: " + d);
    }

    public static void outputCharAnswer(char c)
    {
        System.out.println("RESULT: '" + c + "'");
    }

    public static void outputBooleanAnswer(boolean b)
    {
        System.out.println("RESULT: " + b);
    }

    public static void reportBadInput()
    {
        System.out.println("User entered bad input.");
    }
}