How to convert boolean array to byte array

Question

I wrote this function:

public static boolean[] convertByteArrayToBoolArray(byte[] byteArr) {

    int numberOfBits = (byteArr.length) * 8;

    boolean[] boolArr = new boolean[numberOfBits];

    int j =0;

    for(int i=0; i<byteArr.length; i++){

        Byte value = byteArr[i];

        boolArr[7+j] = ((value & 0x01) != 0);
        boolArr[6+j] = ((value & 0x02) != 0);
        boolArr[5+j] = ((value & 0x04) != 0);
        boolArr[4+j] = ((value & 0x08) != 0);
        boolArr[3+j] = ((value & 0x10) != 0);
        boolArr[2+j] = ((value & 0x20) != 0);
        boolArr[1+j] = ((value & 0x40) != 0);
        boolArr[0+j] = ((value & 0x80) != 0);

        j+= 8;
    }

    return boolArr;
}

how would i go about reversing this. A function which receives boolean[] and returns byte[]?

I would write those 8 assignments in a loop as well, this is a lot of copy-paste code. — martijnn2008
– martijnn2008, Commented Jan 16, 2015 at 19:26
What have you tried? What part of the supplied code doesn't make sense to you? Also, why are you doing it? — DaaaahWhoosh
– DaaaahWhoosh, Commented Jan 16, 2015 at 19:45

arshajii · Accepted Answer · 2015-01-16 19:29:56Z

1

You could try something like this:

private static byte boolsToByte(final boolean[] array, final int start) {
    byte b = 0;
    for (int i = 0; i < 8; i++) {
        if (array[start + i])
            b |= 1 << (7 - i);
    }
    return b;
}

public static byte[] convertBoolArrayToByteArray(boolean[] boolArr) {
    byte[] byteArr = new byte[boolArr.length/8];
    for (int i = 0; i < byteArr.length; i++)
        byteArr[i] = boolsToByte(boolArr, 8*i);
    return byteArr;
}

edited Jan 16, 2015 at 19:29

answered Jan 16, 2015 at 19:23

arshajii

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