Java atoi atoi(String s, int pos, int base)

Description

Method to parse the number in a string.

License

Open Source License

Parameter

Parameter	Description
s	the string with a number in it.
pos	the starting position in the string to find the number.
base	the forced base of the number (0 to determine it automatically).

Return

the numeric value.

Declaration

public static int atoi(String s, int pos, int base) 

Method Source Code

//package com.java2s;
/* -*- tab-width: 4 -*-/*from  www  .  java  2 s .c om*/
 *
 * Electric(tm) VLSI Design System
 *
 * File: TextUtils.java
 *
 * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.
 *
 * Electric(tm) is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * Electric(tm) is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Electric(tm); see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, Mass 02111-1307, USA.
 */

public class Main {
    /**
     * Method to parse the number in a string.
     * <P>
     * There are many reasons to use this method instead of Integer.parseInt...
     * <UL>
     * <LI>This method can handle any radix.
     *     If the number begins with "0", presume base 8.
     *     If the number begins with "0b", presume base 2.
     *     If the number begins with "0x", presume base 16.
     *     Otherwise presume base 10.
     * <LI>This method can handle numbers that affect the sign bit.
     *     If you give 0xFFFFFFFF to Integer.parseInt, you get a numberFormatPostFix exception.
     *     This method properly returns -1.
     * <LI>This method does not require that the entire string be part of the number.
     *     If there is extra text after the end, Integer.parseInt fails (for example "123xx").
     * <LI>This method does not throw an exception if the number is invalid (or blank).
     * </UL>
     * @param s the string with a number in it.
     * @return the numeric value.
     */
    public static int atoi(String s) {
        return atoi(s, 0, 0);
    }

    /**
     * Method to parse the number in a string.
     * See the comments for "atoi(String s)" for reasons why this method exists.
     * @param s the string with a number in it.
     * @param pos the starting position in the string to find the number.
     * @return the numeric value.
     */
    public static int atoi(String s, int pos) {
        return atoi(s, pos, 0);
    }

    /**
     * Method to parse the number in a string.
     * See the comments for "atoi(String s)" for reasons why this method exists.
     * @param s the string with a number in it.
     * @param pos the starting position in the string to find the number.
     * @param base the forced base of the number (0 to determine it automatically).
     * @return the numeric value.
     */
    public static int atoi(String s, int pos, int base) {
        int num = 0;
        int sign = 1;
        int len = s.length();
        if (pos < len && s.charAt(pos) == '-') {
            pos++;
            sign = -1;
        }
        if (base == 0) {
            base = 10;
            if (pos < len && s.charAt(pos) == '0') {
                pos++;
                base = 8;
                if (pos < len && (s.charAt(pos) == 'x' || s.charAt(pos) == 'X')) {
                    pos++;
                    base = 16;
                } else if (pos < len && (s.charAt(pos) == 'b' || s.charAt(pos) == 'B')) {
                    pos++;
                    base = 2;
                }
            }
        }
        for (; pos < len; pos++) {
            char cat = s.charAt(pos);
            int digit = Character.digit(cat, base);
            if (digit < 0) {
                break;
            }
            num = num * base + digit;
            //          if ((cat >= 'a' && cat <= 'f') || (cat >= 'A' && cat <= 'F'))
            //          {
            //             if (base != 16) break;
            //             num = num * 16;
            //             if (cat >= 'a' && cat <= 'f') num += cat - 'a' + 10; else
            //                num += cat - 'A' + 10;
            //             continue;
            //          }
            //         if (!TextUtils.isDigit(cat)) break;
            //         if (cat >= '8' && base == 8) break;
            //         num = num * base + cat - '0';
        }
        return (num * sign);
    }

    private static int digit(char ch) {
        if (ch < '\u0080') {
            return ch >= '0' && ch <= '9' ? ch - '0' : -1;
        }
        return Character.digit((int) ch, 10);
    }
}

Related

1. atoi(Object s)
2. atoi(String s)
3. atoi(String s)
4. atoi(String s)
5. atoi(String s)
6. atoi(String str)
7. atoi(String str)
8. atoi(String[] s)