Creates a BitSet representation of a given long - Java java.util

Java examples for java.util:BitSet

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Description

Creates a BitSet representation of a given long

Demo Code

/*//from  ww w. j  a  v  a2  s .com
 * Copyright (c) 2012 The Broad Institute
 * 
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
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 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is 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 THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
 * THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
//package com.java2s;
import java.util.BitSet;
import java.util.HashMap;
import java.util.Map;

public class Main {
    public static void main(String[] argv) throws Exception {
        long number = 2;
        System.out.println(bitSetFrom(number));
    }

    static final private byte NBITS_LONG_REPRESENTATION = 64;
    static final private byte NBITS_SHORT_REPRESENTATION = 16;
    private static final Map<Short, BitSet> shortCache = new HashMap<Short, BitSet>(
            2 * Short.MAX_VALUE);

    /**
     * Creates a BitSet representation of a given long
     *
     * @param number the number to turn into a bitset
     * @return a bitset representation of the long
     */
    public static BitSet bitSetFrom(long number) {
        return bitSetFrom(number, NBITS_LONG_REPRESENTATION);
    }

    /**
     * Creates a BitSet representation of a given short
     *
     * @param number the number to turn into a bitset
     * @return a bitset representation of the short
     */
    public static BitSet bitSetFrom(short number) {
        BitSet result = shortCache.get(number);
        if (result == null) {
            result = bitSetFrom(number, NBITS_SHORT_REPRESENTATION);
            shortCache.put(number, result);
        }
        return result;
    }

    /**
     * Creates a BitSet representation of an arbitrary integer (number of bits capped at 64 -- long precision)
     *
     * @param number the number to turn into a bitset
     * @param nBits  the number of bits to use as precision for this conversion
     * @return a bitset representation of the integer
     */
    public static BitSet bitSetFrom(long number, int nBits) {
        BitSet bitSet = new BitSet(nBits);
        boolean isNegative = number < 0;
        int bitIndex = 0;
        while (number != 0) {
            if (number % 2 != 0)
                bitSet.set(bitIndex);
            bitIndex++;
            number /= 2;
        }
        if (isNegative) {
            boolean foundFirstSetBit = false;
            for (int i = bitSet.nextSetBit(0); i < nBits && i >= 0; i++) {
                boolean bit = bitSet.get(i);
                if (!foundFirstSetBit && bit)
                    foundFirstSetBit = true; // maintain all bits until the first 1 is found (inclusive)
                else if (foundFirstSetBit)
                    bitSet.flip(i); // flip every other bit up to NBITS_REPRESENTATION
            }
        }
        return bitSet;
    }
}

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