Why is Java boolean size not defined?
see size of boolean is not defined. Below are two statements I see at java primitive data size
not precisely defined
Further explanation says
boolean represents one bit of information, but its "size" isn't something that's precisely defined. Question came to my mind was why booleans in java can't be represented with 1 bit(or 1 byte if byte is the minimum representation ) ?
But I see it has been already answered at https://stackoverflow.com/questions/1907318/why-is-javas-boolean-primitive-size-not-defined where it says
The JVM uses a 32-bit stack cell, used to hold local variables, method arguments, and expression values. Primitives that are smaller than 1 cell are padded out, primitives larger than 32 bits (long and double) take 2 cells
Does it mean even byte/char/short primitive data types also take 32 bit though their size is defined as 8/16/16 bit ?
Also can we say boolean size will be 32 bit on 32 bit cpu and 64 bit on 64 bit cpu ?
TL;DR The only thing that's sure is that java boolean size occupies at least one bit. Everything else depends on the JVM implementation.
The Java Language Specification doesn't define sizes, only value ranges (see The Language Spec). So, it's not only the boolean size that's undefined at this level. And boolean has two possible values: false and true. The Virtual Machine Specification tells us that boolean variables are treated like int with values 0 and 1. Only arrays of boolean have specific support. So at the Virtual Machine level, a boolean variable occupies the same amount of space as an int, meaning one stack cell: at least 4 bytes, typically 4 bytes on 32-bit Java and 8 bytes on 64-bit. Finally there's the HotSpot engine that compiles JVM bytecode into optimised CPU-specific machine code, and I bet that in many cases it's able to deduce the limited value-range of an int-masked boolean from the context and use a smaller size.