Java BigInteger Calculate parseScaledNonNegativeBigInteger(String str)

Description

parse Scaled Non Negative Big Integer

License

Open Source License

Declaration

public static BigInteger parseScaledNonNegativeBigInteger(String str) throws NumberFormatException 

Method Source Code

//package com.java2s;
/*******************************************************************************
 * Copyright (c) 2014 Liviu Ionescu.//from   ww w  . j  a v a2s.  c om
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     Liviu Ionescu - initial version 
 *******************************************************************************/

import java.math.BigInteger;

public class Main {
    public static BigInteger parseScaledNonNegativeBigInteger(String str) throws NumberFormatException {

        str = adjustForSign(str);
        int radix = computeRadix(str);
        str = adjustForRadix(str);
        long scale = computeScale(str);
        str = adjustForScale(str, scale);

        BigInteger value = new BigInteger(str, radix);
        if (scale != 1) {
            value = value.multiply(new BigInteger(String.valueOf(scale)));
        }
        return value;
    }

    private static String adjustForSign(String str) {

        if (str.startsWith("+")) {
            return str.substring(1);
        }

        return str;
    }

    private static int computeRadix(String str) {

        int radix = 10;
        if ((str.startsWith("0x")) || (str.startsWith("0X"))) {
            radix = 16;
        } else if ((str.startsWith("0b")) || (str.startsWith("0B"))) {
            radix = 2;
        } else if (str.startsWith("#")) {
            radix = 2;
        }

        return radix;
    }

    private static String adjustForRadix(String str) {

        if ((str.startsWith("0x")) || (str.startsWith("0X"))) {
            return str.substring(2); // Skip 0x, 0X
        } else if ((str.startsWith("0b")) || (str.startsWith("0B"))) {
            return str.substring(2); // Skip 0b, 0B
        } else if (str.startsWith("#")) {
            return str.substring(1); // Skip #
        }

        // Decimal numbers have no radix prefix to skip.
        return str;
    }

    private static long computeScale(String str) {

        long scale = 1;
        String lastChar = str.substring(str.length() - 1);
        if (lastChar.matches("[kmgtKMGT]")) {
            lastChar = lastChar.toLowerCase();
            if ("k".equals(lastChar)) {
                scale = 1024;
            } else if ("m".equals(lastChar)) {
                scale = 1024 * 1024;
            } else if ("g".equals(lastChar)) {
                scale = 1024 * 1024 * 1024;
            } else if ("7".equals(lastChar)) {
                scale = 1024 * 1024 * 1024 * 1024;
            }
        }
        return scale;
    }

    private static String adjustForScale(String str, long scale) {
        if (scale != 1) {
            return str.substring(0, str.length() - 2);
        }
        return str;
    }
}

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