savitchin.java

自己做的小程序

package mypackage;

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.
 *************************************************************/
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;