How can i convert an integer to byte?

Question

I want to know how can i convert an integer to byte theoretically. I mean i don't want to use a predefined program but i want just to know how can i implement it. What i know that from -128 to 127 an integer is the same as byte but the problemes is from 128 to 128 to +infinite and from -129 to -infinite. For example given the following code:

    Integer a = 140;//10001100 this is his binary conversion
    Byte zz = (byte) a.byteValue();
    System.out.println(zz);// result is -116

How that conversion works in java? Thanks in advance

Look at this SO answer http://stackoverflow.com/questions/842817/how-does-java-convert-int-into-byte — Dheeraj Joshi, Jul 24 '13 at 10:05
Bytes are from `-128` to `127`, the `140` overflows to `-116`. — jlordo, Jul 24 '13 at 10:05

score 3 · Answer 1 · edited Jun 20 '20 at 09:12

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That value is out of range of the Byte and hence overflows.

Refer JLS 4.2.1:

The values of the integral types are integers in the following ranges:

For byte, from -128 to 127, inclusive

A byte is 8 bits , the most significant bit specifies the sign of the number and are are encoded in two's complement.

Read this wonderful SO answer for more.

edited Jun 20 '20 at 09:12

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answered Jul 24 '13 at 10:06

AllTooSir

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I know so how can i convert it to byte? – BenMansourNizar Jul 24 '13 at 10:08
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@BenMansourNizar What result do you want ? It can't store 140 ! – AllTooSir Jul 24 '13 at 10:09
@BenMansourNizar, In theory you can create a list when you will put the parts of Byte. But in reality this is integer or long. – Damian Leszczyński - Vash Jul 24 '13 at 10:17

Evgeniy Dorofeev · Answer 2 · 2013-07-24T10:29:44.067

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Byte value binary representation will not change, it will still be 10001100 but it will be interpreted differently, since byte is a signed type in two's complement representation http://en.wikipedia.org/wiki/Twos_complement and since bit 7 is set it means that now it's a negative number -116

edited Jul 24 '13 at 10:29

answered Jul 24 '13 at 10:14

Evgeniy Dorofeev

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score 1 · Answer 3 · answered Jul 24 '13 at 10:18

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when you are narrowing a primitive, you must explicitly make a cast - so you acknowledge a possible loss of data.

There is no loss if value is within the -128...127 byte value range

answered Jul 24 '13 at 10:18

Ruchira Gayan Ranaweera

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score 0 · Answer 4 · answered Jul 24 '13 at 10:40

You can not convert value grate than 127 into byte as it do not have place to store it. As 140 in binary is 10001100 it mean that you need a type that store at lest 8 bits. A byte store 8 bits but one of then is reserved for sign. So you can not fit it into it. You can use short witch store 16 bits (15 and 1 for sign).

The zero in different types expressed in binary;

byte  b = 0b000_0000;
short s = 0b000_0000_0000_0000;
int   i = 0b000_0000_0000_0000_0000_0000_0000_0000;

If you try to declare something like:

byte  b = 0b1000_1100;

The compiler will tall you Type mismatch: cannot convert from int to byte.

How can i convert an integer to byte?

4 Answers4