How to write bytes above 128?

[fatabass]

Regarding the method:

write(byte[], int, int) in for example FileOutputStream class..

byte values are between 0 - 255 where primitive type byte can store up to 128 in java.
This method gets a byte array as an argument.
How am I suppose to put the value 200 in a byte array so that I can write the byte value 200 to an FileOutputStream?

thanks..

[Norm]

Cast the value to byte: (byte)200

[diamonddragon]

If cast, how to know it is 200?

[Norm]

Print it out

[diamonddragon]

(byte)200 = (200 - 127) - (128 + 1) = -56

[Norm]

What is the purpose of the expression you just posted?
The byte data type is signed. Any value > 127 will have the sign bit set and be a negative number.The compiler promotes bytes to ints which spreads the sign bit. If you want an unsigned value from a byte AND it with 0xFF

[diamonddragon]

Any value >127 will not be a negative number.
(byte)300 = 44

[Norm]

a byte has 8 bits. The max unsigned value it can hold is 255

[diamonddragon]

OK, and my question was what if array need to have negative values, and You insert number (byte)200, how to know it is 200?

[Norm]

As the saying goes, You can not have your cake and eat it too.
You can either treat the byte array as containing unsigned bytes with values from 0 to 255
or it can contain signed bytes with values from -128 to 127.

But not both.

[diamonddragon]

Say there is array of byte, length 5 rows x 2 columns
new byte[5][2]
and say byte[0][1] = (int)(200 / 127) which is flag 1, that indicate value byte[0][0] is actually 256 + byte[0][0], or 256 + (-56) = 200
Or something like that?

[Norm]

Not sure I understand what you are trying to say.
Each element in a byte array is a byte.

[diamonddragon]

This idea is about 2 dimension byte array can represent max value 2⁷ * 2⁸ - 1 = 32767, using flag as above.

[JosAH]

You essentially don't write positive or negative byte values to a stream, you write eight bit patterns instead; it's only how you interpret those patterns, e.g. if you write the pattern 11111111 you may interpret the pattern as -1 or as 255 but the stream doesn't care ... the Java language compiler may protest but a simple cast to a byte type will make it keep its mouth shut.

kind regards,

Jos

[Norm]

2 dimension byte array can represent max value

Why the 2 dim array? The array holds 4 bytes, with 4 bits used as the sign. Why not use an int with only 1 bit used for sign?

[diamonddragon]

Why the 2 dim array? The array holds 4 bytes, with 4 bits used as the sign. Why not use an int with only 1 bit used for sign?

Question was is it possible to put value > 255 into signed byte.
Like is it possible to put 20 people in 4 seats car. :)
Of course int can be used, as a bus can be used.

[Norm]

Question was is it possible to put value > 255 into signed byte.

That is a very clear question after much wandering around. The answer is NO.