java實現位圖（bitmap）

//位圖下標從0開始
public class BitMap {


    //默認256的大小
    private int size = 256;

    private byte[] bits;


    public BitMap(int size) {
        if (size < 0) {
            size = 256;
        }
        this.size = size;
        this.bits = new byte[getindex(size) + 1];
    }

    public BitMap() {
        this.bits = new byte[getindex(256) + 1];
    }

    //獲取對應的下標
    private int getindex(int index) {
        return index >> 3;
    }


    //獲取對應的位數
    private int getBitIndex(int index) {
        return index & 0x07;
    }

    /**
     * 獲取index上的值
     * @param index
     * @return
     */
    public boolean getResult(int index) {
        if (index > size-1 || index < 0) {
            throw new ArrayIndexOutOfBoundsException();
        }
        return (bits[getindex(index)] & (1 << getBitIndex(index))) != 0;
    }

    /**
     * 設置index位置爲0或1
     * @param index
     * @param value
     */
    public void add(int index, boolean value) {
        if (index > size-1 || index < 0) {
            throw new ArrayIndexOutOfBoundsException();
        }
        if (value) {
            bits[getindex(index)] |= 1 << getBitIndex(index);
        }else {
            bits[getindex(index)] &= ~(1 << getBitIndex(index));
        }
    }

}