Java Base Convert fromBase26(String number)

Description

Convert a base-26 representation into a number, considering it to represent a value in base-26 using the characters a-z or A-Z - the string is treated case-insensitively.

License

Open Source License

Parameter

Parameter	Description
number	a string representing a base-26 number

Exception

Parameter	Description
NumberFormatException	if the string does not represent an alphabetical base-26 number

Return

the number represented

Declaration

public static int fromBase26(String number) throws NumberFormatException

Method Source Code

//package com.java2s;
/*//ww w.j  a v  a 2  s  . c  o m
    
Copyright (c) 2000-2014 Board of Trustees of Leland Stanford Jr. University,
all rights reserved.
    
Permission is hereby granted, free of charge, to any person obtaining a copy
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furnished to do so, subject to the following conditions:
    
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
    
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
STANFORD UNIVERSITY BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
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Except as contained in this notice, the name of Stanford University shall not
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*/

public class Main {
    /**
     * Convert a base-26 representation into a number, considering it to represent
     * a value in base-26 using the characters a-z or A-Z - the string is treated
     * case-insensitively. The string is lower cased before the increment is
     * applied. An exception will be thrown if any character is outside of a-z
     * after lower casing.
     * <p>
     * Adapted from http://en.wikipedia.org/wiki/Hexavigesimal.
     * @param number a string representing a base-26 number
     * @return the number represented
     * @throws NumberFormatException if the string does not represent an alphabetical base-26 number
     */
    public static int fromBase26(String number) throws NumberFormatException {
        if (!number.matches("^[a-zA-Z]*$"))
            throw new NumberFormatException("Non-alphabetic characters in string.");

        int s = 0;
        if (number != null && number.length() > 0) {
            number = number.toLowerCase();
            s = (number.charAt(0) - 'a');
            for (int i = 1; i < number.length(); i++) {
                s *= 26;
                s += (number.charAt(i) - 'a');
            }
        }
        return s;
    }
}