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If I have an integer that I'd like to perform bit manipulation on, how can I load it into a java.util.BitSet ? How can I convert it back to an int or long? I'm not so concerned about the size of the BitSet -- it will always be 32 or 64 bits long. I'd just like to use the set() , clear() , nextSetBit() , and nextClearBit() methods rather than bitwise operators, but I can't find an easy way to initialize a bit set with a numeric type.

The following code creates a bit set from a long value and vice versa:

public class Bits {
  public static BitSet convert(long value) {
    BitSet bits = new BitSet();
    int index = 0;
    while (value != 0L) {
      if (value % 2L != 0) {
        bits.set(index);
      ++index;
      value = value >>> 1;
    return bits;
  public static long convert(BitSet bits) {
    long value = 0L;
    for (int i = 0; i < bits.length(); ++i) {
      value += bits.get(i) ? (1L << i) : 0L;
    return value;
EDITED: Now both directions, @leftbrain: of cause, you are right
Add to finnw answer: there are also BitSet.valueOf(long[]) and BitSet.toLongArray(). So:
int n = 12345;
BitSet bs = BitSet.valueOf(new long[]{n});
long l = bs.toLongArray()[0];
                If the bitset has no "1", bs.toLongArray()[0] will throw ArrayIndexOutOfBoundsException exception!
– Qianyue
                Sep 14, 2021 at 8:17
BitSet bitSet = IntStream.range(0, Long.SIZE - 1)
        .filter(i -> 0 != (l & 1L << i))
        .collect(BitSet::new, BitSet::set, BitSet::or);
N.B.: Using BitSet::valueOf and BitSet::toLongArray is of course easier.
                This will fail for a BitSet larger than 32 or 64 bits, in such a case you'll need to handle an int[] or long[] at the output. But OP explicitly doesn't care, so fair enough. Just a few minor glitches: in case of a long you should 1L << i, to prevent overflow, and an OR like value |= 1L << i is enough.
– charlie
                Jul 4, 2016 at 12:46
                That sets one single bit with the index you provide.  I'd like to set each bit that's set in the integer.
– ataylor
                Mar 18, 2010 at 22:17
        
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