Question

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In Java, what is the best way to determine the size of an object?

In Actionscript I can usually just do:

var myVar:uint = 5;
getSize(myVar)
//outputs 4 bytes

How do I do this in Java?

Answer 1

If you turn off -XX:-UseTLAB you can check the Runtime.freeMemory() before and after. However in the case of local variables, they don’t take space on the heap (as they use the stack) and you can’t get it size.

However, an int is a 32-bit sign value and you can expect it will use 4-bytes (or more depending on the JVM and the stack alignment etc)

The sizeof in C++ is useful for pointer arithmetic. Since Java doesn’t allow this, its isn’t useful and possibly deliberately hidden to avoid developers worrying about low level details.