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Looking at this C# code:
byte x = 1; byte y = 2; byte z = x + y; // ERROR: Cannot implicitly convert type 'int' to 'byte' The result of any math performed on byte (or short) types is implicitly cast back to an integer. The solution is to explicitly cast the result back to a byte:
byte z = (byte)(x + y); // this works What I am wondering is why? Is it architectural? Philosophical?
We have:
int + int = int long + long = long float + float = float double + double = double So why not:
byte + byte = byte short + short = short?A bit of background: I am performing a long list of calculations on "small numbers" (i.e. < 8) and storing the intermediate results in a large array. Using a byte array (instead of an int array) is faster (because of cache hits). But the extensive byte-casts spread through the code make it that much more unreadable.
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Performance-wise, an int is faster in almost all cases. The CPU is designed to work efficiently with 32-bit values. Shorter values are complicated to deal with. To read a single byte, say, the CPU has to read the 32-bit block that contains it, and then mask out the upper 24 bits.
A byte is the format data is stored in memory in past. 8 bits. An int is a format likewise you get it as value from the accumulator.
The byte data type in Java is a signed integer based on the two's complement 8-bit mechanism. It is different from the int data type that uses 4 bytes (i.e., 32-bit to store a number). The values that can be stored in a single byte are -128 to 127.
The addition of two-byte values in java is the same as normal integer addition. The byte data type is 8-bit signed two's complement integer. It has a minimum value of -128 and a maximum value of 127 (inclusive).
The third line of your code snippet:
byte z = x + y; actually means
byte z = (int) x + (int) y; So, there is no + operation on bytes, bytes are first cast to integers and the result of addition of two integers is a (32-bit) integer.
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