SavitchIn.java

import java.io.*;
import java.util.*;


/**************************************************************
 *Class for simple console input.
 *A class designed primarily for simple keyboard input of the form
 *one input value per line. If the user enters an improper input,
 *i.e., an input of the wrong type or a blank line, then the user
 *is prompted to reenter the input and given a brief explanation
 *of what is required. Also includes some additional methods to
 *input single numbers, words, and characters, without going to
 *the next line.
 *from:
 * Walter Savitch:
 * "Java - an Introduction to Computer Science & Programming"
 * Prentice Hall 2001
 *************************************************************/
public class SavitchIn
{

    /**********************************************************
     *Reads a line of text and returns that line as a String value.
     *The end of a line must be indicated either by a new-line
     *character '\n' or by a carriage return '\r' followed by a
     *new-line character '\n'. (Almost all systems do this
     *automatically. So, you need not worry about this detail.)
     *Neither the '\n', nor the '\r' if present, are part of the
     *string returned. This will read the rest of a line if the
     *line is already partially read.
     *********************************************************/
    public static String readLine()
    {
        char nextChar;
        String result = "";
        boolean done = false;

        while (!done)
        {
            nextChar = readChar();
            if (nextChar == '\n')
               done = true;
            else if (nextChar == '\r')
            {
                //Do nothing.
                //Next loop iteration will detect '\n'
            }
            else
               result = result + nextChar;
        }

        return result;
    }


    /*********************************************************
     *Reads the first string of nonwhite characters on a line and
     *returns that string. The rest of the line is discarded. If
     *the line contains only white space, then the user is asked
     *to reenter the line.
     *********************************************************/
    public static String readLineWord()
    {
        String inputString = null,
               result = null;
        boolean done = false;

        while(!done)
        {
            inputString = readLine();
            StringTokenizer wordSource =
                                new StringTokenizer(inputString);
            if (wordSource.hasMoreTokens())
            {
                result = wordSource.nextToken();
                done = true;
            }
            else
            {
                System.out.println(
                       "Your input is not correct. Your input must");
                System.out.println(
                    "contain at least one nonwhitespace character.");
                System.out.println(
                                 "Please, try again. Enter input:");
           }
       }

       return result;
   }


    /**********************************************************
     *Precondition: The user has entered a number of type int on
     *a line by itself, except that there may be white space before
     *and/or after the number.
     *Action: Reads and returns the number as a value of type int.
     *The rest of the line is discarded. If the input is not
     *entered correctly, then in most cases, the user will be
     *asked to reenter the input. In particular, this applies to
     *incorrect number formats and blank lines.
     *********************************************************/
    public static int readLineInt()
    {
        String inputString = null;
        int number = -9999;//To keep the compiler happy.
                           //Designed to look like a garbage value.
        boolean done = false;

        while (! done)
        {
            try
            {
                inputString = readLine();
                inputString = inputString.trim();
                number = Integer.parseInt(inputString);
                done = true;
            }
            catch (NumberFormatException e)
            {
                System.out.println(
                                "Your input number is not correct.");
                System.out.println("Your input number must be");
                System.out.println("a whole number written as an");
                System.out.println("ordinary numeral, such as 42");
                System.out.println("Minus signs are OK,"
                               + "but do not use a plus sign.");
                System.out.println("Please, try again.");
                System.out.println("Enter a whole number:");
            }
        }

        return number;
    }


     /*********************************************************
     *Precondition: The user has entered a number of type long on
     *a line by itself, except that there may be white space
     *before and/or after the number.
     *Action: Reads and returns the number as a value of type
     *long. The rest of the line is discarded. If the input is not
     *entered correctly, then in most cases, the user will be asked
     *to reenter the input. In particular, this applies to
     *incorrect number formats and blank lines.
     ********************************************************/
    public static long readLineLong()
    {
        String inputString = null;
        long number = -9999;//To keep the compiler happy.
                            //Designed to look like a garbage value.
        boolean done = false;

        while (! done)
        {
            try
            {
                inputString = readLine();
                inputString = inputString.trim();
                number = Long.parseLong(inputString);
                done = true;
            }
            catch (NumberFormatException e)
            {
                System.out.println(
                                "Your input number is not correct.");
                System.out.println("Your input number must be");
                System.out.println("a whole number written as an");
                System.out.println("ordinary numeral, such as 42");
                System.out.println("Minus signs are OK,"
                               + "but do not use a plus sign.");
                System.out.println("Please, try again.");
                System.out.println("Enter a whole number:");
            }
       }

        return number;
    }


     /********************************************************
     *Precondition: The user has entered a number of type double
     *on a line by itself, except that there may be white space
     *before and/or after the number.
     *Action: Reads and returns the number as a value of type
     *double. The rest of the line is discarded. If the input is
     *not entered correctly, then in most cases, the user will be
     *asked to reenter the input. In particular, this applies to
     *incorrect number formats and blank lines.
     *********************************************************/
    public static double readLineDouble()
    {
        String inputString = null;
        double number = -9999;//To keep the compiler happy.
                              //Designed to look like a garbage value.
        boolean done = false;

        while (! done)
        {
            try
            {
                inputString = readLine();
                inputString = inputString.trim();
                number = Double.parseDouble(inputString);
                done = true;
            }
            catch (NumberFormatException e)
            {
                System.out.println(
                                "Your input number is not correct.");
                System.out.println("Your input number must be");
                System.out.println("an ordinary number either with");
                System.out.println("or without a decimal point,");
                System.out.println("such as 42 or 9.99");
                System.out.println("Please, try again.");
                System.out.println("Enter the number:");
            }
        }

        return number;
    }


     /*********************************************************
     *Precondition: The user has entered a number of type float
     *on a line by itself, except that there may be white space
     *before and/or after the number.
     *Action: Reads and returns the number as a value of type
     *float. The rest of the line is discarded. If the input is
     *not entered correctly, then in most cases, the user will
     *be asked to reenter the input. In particular,
     *this applies to incorrect number formats and blank lines.
     *********************************************************/
    public static float readLineFloat()
    {
        String inputString = null;
        float number = -9999;//To keep the compiler happy.
                              //Designed to look like a garbage value.
        boolean done = false;

        while (! done)
        {
            try
            {
                inputString = readLine();
                inputString = inputString.trim();
                number = Float.parseFloat(inputString);
                done = true;
            }
            catch (NumberFormatException e)
            {
                System.out.println(
                                "Your input number is not correct.");
                System.out.println("Your input number must be");
                System.out.println("an ordinary number either with");
                System.out.println("or without a decimal point,");
                System.out.println("such as 42 or 9.99");
                System.out.println("Please, try again.");
                System.out.println("Enter the number:");
            }
        }

        return number;
    }


     /*********************************************************
     *Reads the first nonwhite character on a line and returns
     *that character. The rest of the line is discarded. If the
     *line contains only white space, then the user is asked to
     *reenter the line.
     *********************************************************/
    public static char readLineNonwhiteChar()
    {
        boolean done = false;
        String inputString = null;
        char nonWhite = ' ';//To keep the compiler happy.

        while (! done)
        {
            inputString = readLine();
            inputString = inputString.trim();
            if (inputString.length() == 0)
            {
                System.out.println(
                                "Your input is not correct.");
                System.out.println("Your input must contain at");
                System.out.println(
                              "least one nonwhitespace character.");
                System.out.println("Please, try again.");
                System.out.println("Enter input:");
            }
            else
            {
                nonWhite = (inputString.charAt(0));
                done = true;
            }
        }

        return nonWhite;
    }


    /********************************************************
     *Input should consist of a single word on a line, possibly
     *surrounded by white space. The line is read and discarded.
     *If the input word is "true" or "t", then true is returned.
     *If the input word is "false" or "f", then false is returned.
     *Uppercase and lowercase letters are considered equal. If the
     *user enters anything else (e.g., multiple words or different
     *words), then the user is asked to reenter the input.
     ********************************************************/
    public static boolean readLineBoolean()
    {
        boolean done = false;
        String inputString = null;
        boolean result = false;//To keep the compiler happy.

        while (! done)
        {
            inputString = readLine();
            inputString = inputString.trim();
            if (inputString.equalsIgnoreCase("true")
                   || inputString.equalsIgnoreCase("t"))
            {
                result = true;
                done = true;
            }
            else if (inputString.equalsIgnoreCase("false")
                        || inputString.equalsIgnoreCase("f"))
            {
                result = false;
                done = true;
            }
            else
            {
                System.out.println(
                                "Your input number is not correct.");
                System.out.println("Your input must be");
                System.out.println("one of the following:");
                System.out.println("the word true,");
                System.out.println("the word false,");
                System.out.println("the letter T,");
                System.out.println("or the letter F.");
                System.out.println("You may use either upper-");
                System.out.println("or lowercase letters.");
                System.out.println("Please, try again.");
                System.out.println("Enter input:");
            }
         }

        return result;
    }


    /********************************************************
     *Reads the next input character and returns that character. The
     *next read takes place on the same line where this one left off.
     ********************************************************/
    public static char readChar()
    {
        int charAsInt = -1; //To keep the compiler happy
        try
        {
            charAsInt = System.in.read();
        }
        catch(IOException e)
        {
            System.out.println(e.getMessage());
            System.out.println("Fatal error. Ending Program.");
            System.exit(0);
        }

        return (char)charAsInt;
    }


    /*******************************************************
     *Reads the next nonwhite input character and returns that
     *character. The next read takes place immediately after
     *the character read.
     *******************************************************/
    public static char readNonwhiteChar()
    {
      char next;

      next =  readChar();
      while (Character.isWhitespace(next))
          next =  readChar();

      return next;
    }


    /**********************************************************
     *The following methods are not used in the text, except for
     *a brief reference in Chapter 2. No program code uses them.
     *However, some programmers may want to use them.
     *********************************************************/


    /**********************************************************
     *Precondition: The next input in the stream consists of an
     *int value, possibly preceded by white space, but definitely
     *followed by white space.
     *Action: Reads the first string of nonwhite characters
     *and returns the int value it represents. Discards the first
     *whitespace character after the word. The next read takes
     *place immediately after the discarded whitespace.
     *In particular, if the word is at the end of a line, the
     *next reading will take place starting on the next line.
     *If the next word does not represent an int value,
     *a NumberFormatException is thrown.
     *********************************************************/
    public static int readInt() throws NumberFormatException
    {
        String inputString = null;
        inputString = readWord();
        return Integer.parseInt(inputString);
    }



    /**********************************************************
     *Precondition: The next input consists of a long value,
     *possibly preceded by white space, but definitely
     *followed by white space.
     *Action: Reads the first string of nonwhite characters and
     *returns the long value it represents. Discards the first
     *whitespace character after the string read. The next read
     *takes place immediately after the discarded whitespace.
     *In particular, if the string read is at the end of a line,
     *the next reading will take place starting on the next line.
     *If the next word does not represent a long value,
     *a NumberFormatException is thrown.
     **********************************************************/
    public static long readLong()
                      throws NumberFormatException
    {
        String inputString = null;
        inputString = readWord();
        return Long.parseLong(inputString);
    }


   /**********************************************************
     *Precondition: The next input consists of a double value,
     *possibly preceded by white space, but definitely
     *followed by white space.
     *Action: Reads the first string of nonwhitespace characters
     *and returns the double value it represents. Discards the
     *first whitespace character after the string read. The next
     *read takes place immediately after the discarded whitespace.
     *In particular, if the string read is at the end of a line,
     *the next reading will take place starting on the next line.
     *If the next word does not represent a double value,
     *a NumberFormatException is thrown.
     *********************************************************/
    public static double readDouble()
                       throws NumberFormatException
    {
        String inputString = null;
        inputString = readWord();
        return Double.parseDouble(inputString);
    }




    /*********************************************************
     *Precondition: The next input consists of a float value,
     *possibly preceded by white space, but definitely
     *followed by white space.
     *Action: Reads the first string of nonwhite characters and
     *returns the float value it represents. Discards the first
     *whitespace character after the string read. The next read
     *takes place immediately after the discarded whitespace.
     *In particular, if the string read is at the end of a line,
     *the next reading will take place starting on the next line.
     *If the next word does not represent a float value,
     *a NumberFormatException is thrown.
     *********************************************************/
    public static float readFloat()
                         throws NumberFormatException
    {
        String inputString = null;
        inputString = readWord();
        return Float.parseFloat(inputString);
    }


   /**********************************************************
     *Reads the first string of nonwhite characters and returns
     *that string. Discards the first whitespace character after
     *the string read. The next read takes place immediately after
     *the discarded whitespace. In particular, if the string
     *read is at the end of a line, the next reading will take
     *place starting on the next line. Note, that if it receives
     *blank lines, it will wait until it gets a nonwhitespace
     *character.
     *********************************************************/
    public static String readWord()
    {
        String result = "";
        char next;

        next =  readChar();
        while (Character.isWhitespace(next))
             next =  readChar();

        while (!(Character.isWhitespace(next)))
        {
            result = result + next;
            next =  readChar();
        }

        if (next == '\r')
        {
            next = readChar();
            if (next != '\n')
            {
                System.out.println(
                    "Fatal Error in method readWord of class SavitchIn.");
                System.exit(1);
            }
        }

        return result;
    }


    /*********************************************************
     *Precondition: The user has entered a number of type byte on
     *a line by itself, except that there may be white space before
     *and/or after the number.
     *Action: Reads and returns the number as a value of type byte.
     *The rest of the line is discarded. If the input is not
     *entered correctly, then in most cases, the user will be
     *asked to reenter the input. In particular, this applies to
     *incorrect number formats and blank lines.
     *********************************************************/
    public static byte readLineByte()
    {
        String inputString = null;
        byte number = -123;//To keep the compiler happy.
                           //Designed to look like a garbage value.
        boolean done = false;

        while (! done)
        {
            try
            {
                inputString = readLine();
                inputString = inputString.trim();
                number = Byte.parseByte(inputString);
                done = true;
            }
            catch (NumberFormatException e)
            {
                System.out.println(
                                "Your input number is not correct.");
                System.out.println("Your input number must be a");
                System.out.println("whole number in the range");
                System.out.println("-128 to 127, written as");
                System.out.println("an ordinary numeral, such as 42.");
                System.out.println("Minus signs are OK,"
                               + "but do not use a plus sign.");
                System.out.println("Please, try again.");
                System.out.println("Enter a whole number:");
            }
        }

        return number;
    }


    /*********************************************************
     *Precondition: The user has entered a number of type short on
     *a line by itself, except that there may be white space before
     *and/or after the number.
     *Action: Reads and returns the number as a value of type short.
     *The rest of the line is discarded. If the input is not
     *entered correctly, then in most cases, the user will be
     *asked to reenter the input. In particular, this applies to
     *incorrect number formats and blank lines.
     ********************************************************/
    public static short readLineShort()
    {
        String inputString = null;
        short number = -9999;//To keep the compiler happy.
                           //Designed to look like a garbage value.
        boolean done = false;

        while (! done)
        {
            try
            {
                inputString = readLine();
                inputString = inputString.trim();
                number = Short.parseShort(inputString);
                done = true;
            }
            catch (NumberFormatException e)
            {
                System.out.println(
                                "Your input number is not correct.");
                System.out.println("Your input number must be a");
                System.out.println("whole number in the range");
                System.out.println("-32768 to 32767, written as");
                System.out.println("an ordinary numeral, such as 42.");
                System.out.println("Minus signs are OK,"
                               + "but do not use a plus sign.");
                System.out.println("Please, try again.");
                System.out.println("Enter a whole number:");
            }
        }

        return number;
    }


    public static byte readByte() throws NumberFormatException
    {
        String inputString = null;
        inputString = readWord();
        return Byte.parseByte(inputString);
    }


    public static short readShort() throws NumberFormatException
    {
        String inputString = null;
        inputString = readWord();
        return Short.parseShort(inputString);
    }


    //The following was intentionally not used in the code for
    //other methods so that somebody reading the code could more
    //quickly see what was being used.
    /*********************************************************
     *Reads the first byte in the input stream and returns that
     *byte as an int. The next read takes place where this one
     *left off. This read is the same as System.in.read(),
     *except that it catches IOExceptions.
     ********************************************************/
    public static int read()
    {
        int result = -1; //To keep the compiler happy
        try
        {
            result = System.in.read();
        }
        catch(IOException e)
        {
            System.out.println(e.getMessage());
            System.out.println("Fatal error. Ending Program.");
            System.exit(0);
        }
        return result;
    }
}