@Muhammad Ali Khojaye
I think its JVM dependent feature, but since it represents only 1 bit of information , it should be of size 1-bit.
But may be JVM has to store something else in it .....So the size may vary i think.
The tutorial is correct; the "size" of a boolean can vary from one implementation to another. It is only necessary to use 1 bit, but that leaves at least 7 bits in the byte which cannot be used. So it might be easier to use all 8 bits.