Java BigInteger Create createBigInteger(final String str)

Description

Convert a String to a BigInteger; since 3.2 it handles hex (0x or #) and octal (0) notations.

Returns null if the string is null.

License

Apache License

Parameter

Parameter	Description
str	a <code>String</code> to convert, may be null

Exception

Parameter	Description
NumberFormatException	if the value cannot be converted

Return

converted BigInteger (or null if the input is null)

Declaration

public static BigInteger createBigInteger(final String str)

Method Source Code

//package com.java2s;
/*// ww w . j a v  a  2 s.  c o  m
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.math.BigInteger;

public class Main {
    /**
     * <p>Convert a <code>String</code> to a <code>BigInteger</code>;
     * since 3.2 it handles hex (0x or #) and octal (0) notations.</p>
     *
     * <p>Returns <code>null</code> if the string is <code>null</code>.</p>
     *
     * @param str  a <code>String</code> to convert, may be null
     * @return converted <code>BigInteger</code> (or null if the input is null)
     * @throws NumberFormatException if the value cannot be converted
     */
    public static BigInteger createBigInteger(final String str) {
        if (str == null) {
            return null;
        }
        int pos = 0; // offset within string
        int radix = 10;
        boolean negate = false; // need to negate later?
        if (str.startsWith("-")) {
            negate = true;
            pos = 1;
        }
        if (str.startsWith("0x", pos) || str.startsWith("0x", pos)) { // hex
            radix = 16;
            pos += 2;
        } else if (str.startsWith("#", pos)) { // alternative hex (allowed by Long/Integer)
            radix = 16;
            pos++;
        } else if (str.startsWith("0", pos) && str.length() > pos + 1) { // octal; so long as there are additional digits
            radix = 8;
            pos++;
        } // default is to treat as decimal

        final BigInteger value = new BigInteger(str.substring(pos), radix);
        return negate ? value.negate() : value;
    }
}