java实现BitMap

public class BitMap {

    private byte[] drums;

    public BitMap(){
        this(1024);
    }

    public BitMap(int size){
        if(size <= 0)
            throw new RuntimeException("BitMap长度应该大于0");
        // size & 0x07 == size % 8          size >> 3 == size /= 8
        int drumSize = (size & 0x07) == 0 ? size >> 3: (size >> 3)+1;
        drums = new byte[drumSize];
    }

    public void add(int num){
        int position = findDrumPosition(num);
        drums[position] |= 1 << (num & 0x07);
    }

    public void remove(int num){
        int position = findDrumPosition(num);
        drums[position] &= ~(0 ^ 1 << (num & 0x07));
    }

    public boolean has(int num){
        int position = findDrumPosition(num);
        return ((drums[position] >> (num & 0x07)) & 0x01) == 1;
    }

    public void forEach(Consumer<Integer> exist, Consumer<Integer> noExist){
        if(noExist == null)
            noExist = e->{};
        if(exist == null)
            exist = e->{};
        for (int i = 0; i < drums.length<<3; i++) {
            if(!has(i))
                noExist.accept(i);
            else
                exist.accept(i);
        }
    }

    // 定位桶
    private int findDrumPosition(int num){
        if(num < 0 || num >= drums.length<<3)
            throw new RuntimeException("存入的数据应该大于等于0且小于BitMap的长度");
        return num >> 3;
    }
}