Java Parse Decimal parseDecimal(PushbackReader reader)

Description

parse Decimal

License

Open Source License

Declaration

public static double parseDecimal(PushbackReader reader) throws IOException, ParseException 

Method Source Code

//package com.java2s;
/*//from www  .  j ava2  s .c o  m
 * (c) Copyright 2007 by Volker Bergmann. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, is permitted under the terms of the
 * GNU General Public License.
 *
 * For redistributing this software or a derivative work under a license other
 * than the GPL-compatible Free Software License as defined by the Free
 * Software Foundation or approved by OSI, you must first obtain a commercial
 * license to this software product from Volker Bergmann.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * WITHOUT A WARRANTY OF ANY KIND. ALL EXPRESS OR IMPLIED CONDITIONS,
 * REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE
 * HEREBY EXCLUDED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

import java.io.PushbackReader;
import java.io.IOException;

import java.text.ParseException;
import java.text.ParsePosition;

public class Main {
    public static double parseDecimal(PushbackReader reader) throws IOException, ParseException {
        double result = parseInteger(reader);
        double postfix = parseOptionalPostfix(reader);
        if (result >= 0)
            result += postfix;
        else
            result -= postfix;
        return result;
    }

    public static long parseInteger(PushbackReader reader) throws IOException, ParseException {
        boolean negative = parseOptionalSign(reader);
        return parseNonNegativeInteger(reader) * (negative ? -1 : 1);
    }

    public static double parseOptionalPostfix(PushbackReader reader) throws IOException {
        int c = reader.read();
        if (c != '.') {
            if (c != -1)
                reader.unread(c);
            return 0.;
        }
        double result = 0;
        double base = 0.1;
        while ((c = reader.read()) != -1 && Character.isDigit((char) c)) {
            result += (c - '0') * base;
            base *= 0.1;
        }
        if (c != -1)
            reader.unread(c);
        return result;
    }

    public static boolean parseOptionalSign(PushbackReader reader) throws IOException {
        skipWhitespace(reader);
        int optionalSign = reader.read();
        if (optionalSign == '-')
            return true;
        if (optionalSign != -1)
            reader.unread(optionalSign);
        return false;
    }

    public static long parseNonNegativeInteger(String source, ParsePosition pos) throws ParseException {
        int digit;
        if (pos.getIndex() > source.length() || !Character.isDigit(digit = source.charAt(pos.getIndex())))
            throw new ParseException("Number expected", 0);
        pos.setIndex(pos.getIndex() + 1);
        long result = digit - '0';
        while (pos.getIndex() < source.length() && Character.isDigit(digit = source.charAt(pos.getIndex()))) {
            result = result * 10 + digit - '0';
            pos.setIndex(pos.getIndex() + 1);
        }
        return result;
    }

    public static long parseNonNegativeInteger(PushbackReader reader) throws IOException, ParseException {
        int digit;
        if ((digit = reader.read()) == -1 || !Character.isDigit((char) digit))
            throw new ParseException("Long expected", 0);
        long result = digit - '0';
        while ((digit = reader.read()) != -1 && Character.isDigit((char) digit))
            result = result * 10 + digit - '0';
        if (digit != -1)
            reader.unread(digit);
        return result;
    }

    public static void skipWhitespace(PushbackReader reader) throws IOException {
        int c;
        do {
            c = reader.read();
        } while (c != -1 && Character.isWhitespace((char) c));
        if (c != -1)
            reader.unread(c);
    }

    public static void skipWhiteSpace(String text, ParsePosition pos) {
        int i;
        while ((i = pos.getIndex()) < text.length() && Character.isWhitespace(text.charAt(i)))
            pos.setIndex(i + 1);
    }
}

Related

1. parseBigDecimal(String s, NumberFormat format)
2. parseDecimal(String d)
3. parseDecimal(String text)