创建 BitSet 时是否可以设置位？

Question

I need to create a few BitSets in a loop, something like:

ArrayList<BitSet> bitSetList = new ArrayList<BitSet>();

for (int x : array) {
    bitSetList.add(new BitSet() //and set bits in specific places)
}

Answer 1

(To create a BitSet & set specific bits,) You can use one of:

•  static BitSet valueOf(byte[] bytes) /** Returns a new bit set containing all the bits in the given byte array.**/

•  static BitSet valueOf(long[] longs) /** Returns a new bit set containing all the bits in the given long array.*//

•  static BitSet valueOf(ByteBuffer bb) /** Returns a new bit set containing all the bits in the given byte buffer between its position and limit.**/

•  static BitSet valueOf(LongBuffer lb) /**Returns a new bit set containing all the bits in the given long buffer between its position and limit.**/

API-DOC: https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/BitSet.html

Answer 2

BitSet has several static overloaded methods called valueOf with which you can create a BitSet initalized with the bits set in them, for example a byte array:

BitSet example = BitSet.valueOf(new byte[] { 0b101 });
System.out.println(example.get(0)); // Prints true
System.out.println(example.get(1)); // Prints false
System.out.println(example.get(2)); // Prints true

See: https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/util/BitSet.html#valueOf(byte%5B%5D)

Answer 3

Like any other object in Java, you can create a BitSet object and add it to a List in this manner. Before adding it to the List, I would create the BitSet object and add data to the object.

Answer 4

You can you stream to create a BitSet of each ints like that:

List<Integer> ints = Arrays.asList(1, 8, 15);
List<BitSet> list = ints.stream().map(BitSet::new).collect(Collectors.toList());
System.out.println(list);

The .map(BitSet::new) can be replaced by .map(i -> new BitSet(i)) if you don't like how it's wrote.

Answer 5

You should use BitSet.valueOf() . Just to merry this post. Here is a mess hack.

ArrayList<BitSet> bitSetList = new ArrayList<BitSet>();
        
bitSetList.add(new BitSet() {
    public BitSet setMultiple(final int[] bitArray) {
        for(int i=0; i < bitArray.length; ++i) 
            set(bitArray[i]);
        return this;
    };
}.setMultiple(array));