Full Java Code Listing - How to find the maximum positive integer (whole number) using String concatenation in Java?

Posted Thu, 02/19/2009 - 21:56 by deepak

A full working Java program with its console output for solving the problem - How to find the maximum positive integer (whole number) using StringThe String class represents character strings. All string literals in Java programs, such as "abc", are implemented as instances of this class. Below are all the articles related to String. concatenation in Java ?

Table of Contents [hide]

Introduction
Full Java Program
Program Output

Introduction

This article is about designing and writing a Java program that will take the number of digits as its input and will find the maximum possible whole number with that number of digits. For example,

No of digits (Input)	Maximum Integer (Output)
1	9
5	99999
10	9999999999
50	99999999999999999999999999999999999999999999999999

Full Java Program

/**

 * Copyright www.1your.com

 * 

 * FindMaxIntegerForGivenDigitsUsingStrings.java

 * This is an accompanying program for the article

 * http://www.1your.com/drupal/findmaxintegerinjavausingstringconcatenation 

 */

package com.oneyour.math;

import java.math.BigInteger;

import java.text.ParseException;

/**

 * A Java  program to find the maximum possible Integer with the given number of digits. 

 * For example this program will find the number 9999 for 4 digits and 999999 for 6 digits.

 */

public class FindMaxIntegerForGivenDigitsUsingStrings {

  private FindMaxIntegerForGivenDigitsUsingStrings() 

  {

    // Private constructor as the only method provided by this class is 

    // a static method.

  }

  /**

   * The main method which is the entry point of this program.

   */

  public static void main(String[] args) 

  {

    for (int count = 1; count < 100; count++)

    {

      try 

      {

        String maxNumberByString = findMaxPositiveIntegerByStringConcatenation(count);

        System.out.println("Digits - '" + count + "' -- Max Number - '" 

            + maxNumberByString + "'");

      } 

      catch (ParseException parseException)

      {

        System.err.println("Problems encountered.");

        parseException.printStackTrace();

      }

    }

  }

  /**

   * 

   * @param digits

   *            The number of digits for which the maximum possible integer will be found.

   *            

   * @return

   *            The maximum number (integer) for the given number of digits. 

   * 

   * @throws ParseException

   *            Problems while finding the maximum maximum number (integer) for the given number of digits. 

   * 

   */

  private static String findMaxPositiveIntegerByStringConcatenation(int digits) throws ParseException

  {

    if (digits <= 0)

    {

      // Error condition

      return "-1";

    }

    StringBuilder maxNumberString = new StringBuilder();

    for (int count =0; count < digits; count++)

    {

      maxNumberString.append(9); 

    }

    return new BigInteger((maxNumberString.toString())).toString();

  }

}

Program Output

Digits - '1' -- Max Number - '9'

Digits - '2' -- Max Number - '99'

Digits - '3' -- Max Number - '999'

Digits - '4' -- Max Number - '9999'

Digits - '5' -- Max Number - '99999'

Digits - '6' -- Max Number - '999999'

Digits - '7' -- Max Number - '9999999'

Digits - '8' -- Max Number - '99999999'

Digits - '9' -- Max Number - '999999999'

Digits - '10' -- Max Number - '9999999999'

Digits - '11' -- Max Number - '99999999999'

Digits - '12' -- Max Number - '999999999999'

Digits - '13' -- Max Number - '9999999999999'

Digits - '14' -- Max Number - '99999999999999'

Digits - '15' -- Max Number - '999999999999999'

Digits - '16' -- Max Number - '9999999999999999'

Digits - '17' -- Max Number - '99999999999999999'

Digits - '18' -- Max Number - '999999999999999999'

Digits - '19' -- Max Number - '9999999999999999999'

Digits - '20' -- Max Number - '99999999999999999999'

Digits - '21' -- Max Number - '999999999999999999999'

Digits - '22' -- Max Number - '9999999999999999999999'

Digits - '23' -- Max Number - '99999999999999999999999'

Digits - '24' -- Max Number - '999999999999999999999999'

Digits - '25' -- Max Number - '9999999999999999999999999'

Digits - '26' -- Max Number - '99999999999999999999999999'

Digits - '27' -- Max Number - '999999999999999999999999999'

Digits - '28' -- Max Number - '9999999999999999999999999999'

Digits - '29' -- Max Number - '99999999999999999999999999999'

Digits - '30' -- Max Number - '999999999999999999999999999999'

Digits - '31' -- Max Number - '9999999999999999999999999999999'

Digits - '32' -- Max Number - '99999999999999999999999999999999'

Digits - '33' -- Max Number - '999999999999999999999999999999999'

Digits - '34' -- Max Number - '9999999999999999999999999999999999'

Digits - '35' -- Max Number - '99999999999999999999999999999999999'

Digits - '36' -- Max Number - '999999999999999999999999999999999999'

Digits - '37' -- Max Number - '9999999999999999999999999999999999999'

Digits - '38' -- Max Number - '99999999999999999999999999999999999999'

Digits - '39' -- Max Number - '999999999999999999999999999999999999999'

Digits - '40' -- Max Number - '9999999999999999999999999999999999999999'

Digits - '41' -- Max Number - '99999999999999999999999999999999999999999'

Digits - '42' -- Max Number - '999999999999999999999999999999999999999999'

Digits - '43' -- Max Number - '9999999999999999999999999999999999999999999'

Digits - '44' -- Max Number - '99999999999999999999999999999999999999999999'

Digits - '45' -- Max Number - '999999999999999999999999999999999999999999999'

Digits - '46' -- Max Number - '9999999999999999999999999999999999999999999999'

Digits - '47' -- Max Number - '99999999999999999999999999999999999999999999999'

Digits - '48' -- Max Number - '999999999999999999999999999999999999999999999999'

Digits - '49' -- Max Number - '9999999999999999999999999999999999999999999999999'

Digits - '50' -- Max Number - '99999999999999999999999999999999999999999999999999'

Digits - '51' -- Max Number - '999999999999999999999999999999999999999999999999999'

Digits - '52' -- Max Number - '9999999999999999999999999999999999999999999999999999'

Digits - '53' -- Max Number - '99999999999999999999999999999999999999999999999999999'

Digits - '54' -- Max Number - '999999999999999999999999999999999999999999999999999999'

Digits - '55' -- Max Number - '9999999999999999999999999999999999999999999999999999999'

Digits - '56' -- Max Number - '99999999999999999999999999999999999999999999999999999999'

Digits - '57' -- Max Number - '999999999999999999999999999999999999999999999999999999999'

Digits - '58' -- Max Number - '9999999999999999999999999999999999999999999999999999999999'

Digits - '59' -- Max Number - '99999999999999999999999999999999999999999999999999999999999'

Digits - '60' -- Max Number - '999999999999999999999999999999999999999999999999999999999999'

Digits - '61' -- Max Number - '9999999999999999999999999999999999999999999999999999999999999'

Digits - '62' -- Max Number - '99999999999999999999999999999999999999999999999999999999999999'

Digits - '63' -- Max Number - '999999999999999999999999999999999999999999999999999999999999999'

Digits - '64' -- Max Number - '9999999999999999999999999999999999999999999999999999999999999999'

Digits - '65' -- Max Number - '99999999999999999999999999999999999999999999999999999999999999999'

Digits - '66' -- Max Number - '999999999999999999999999999999999999999999999999999999999999999999'

Digits - '67' -- Max Number - '9999999999999999999999999999999999999999999999999999999999999999999'

Digits - '68' -- Max Number - '99999999999999999999999999999999999999999999999999999999999999999999'

Digits - '69' -- Max Number - '999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '70' -- Max Number - '9999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '71' -- Max Number - '99999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '72' -- Max Number - '999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '73' -- Max Number - '9999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '74' -- Max Number - '99999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '75' -- Max Number - '999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '76' -- Max Number - '9999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '77' -- Max Number - '99999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '78' -- Max Number - '999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '79' -- Max Number - '9999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '80' -- Max Number - '99999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '81' -- Max Number - '999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '82' -- Max Number - '9999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '83' -- Max Number - '99999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '84' -- Max Number - '999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '85' -- Max Number - '9999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '86' -- Max Number - '99999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '87' -- Max Number - '999999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '88' -- Max Number - '9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '89' -- Max Number - '99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '90' -- Max Number - '999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '91' -- Max Number - '9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '92' -- Max Number - '99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '93' -- Max Number - '999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '94' -- Max Number - '9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '95' -- Max Number - '99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '96' -- Max Number - '999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '97' -- Max Number - '9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '98' -- Max Number - '99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Digits - '99' -- Max Number - '999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999'

Categories:
- Java
- Strings
- Mathematics

Comments