Hi I am learning Java basics. I need to check the size of primitive data types like using sizeof(); in c language.
Example code:
int i;
System.out.print(sizeof(i));
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2possible duplicate of In Java, what is the best way to determine the size of an object?Sebastian– Sebastian2015-08-19 11:55:41 +00:00Commented Aug 19, 2015 at 11:55
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3If you type the title of your question into Google the first result gives you the answercodebox– codebox2015-08-19 11:57:24 +00:00Commented Aug 19, 2015 at 11:57
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For which purpose you need this?Tagir Valeev– Tagir Valeev2015-08-19 12:04:56 +00:00Commented Aug 19, 2015 at 12:04
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Not for any specific purpose! Just need to know if any possibilities.Prakash Bala– Prakash Bala2015-08-19 12:06:09 +00:00Commented Aug 19, 2015 at 12:06
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2 Answers
Use the BYTES constants (since Java 8) in the corresponding boxed classes:
sizeof(int) -> Integer.BYTES
sizeof(long) -> Long.BYTES
sizeof(char) -> Character.BYTES
sizeof(short) -> Short.BYTES
sizeof(float) -> Float.BYTES
sizeof(double) -> Double.BYTES
sizeof(byte) -> Byte.BYTES
Note that reference and boolean sizes are not defined, it's implementation-specific. In general you rarely should care about their size.
1 Comment
Jean-François Savard
Pre java-8 you could use the
SIZE constant, just need to know that they give the representation in bits instead of bytes.There's no need for such a thing in Java since the sizes of the primitives are set for all JVMs (unlike C where they can vary).
char is 16 bit (actually an unsigned quantity), int is 32 bit, long is 64 bit.
boolean is the ugly sister in all this. Internally it is manipulated as a 32 bit int, but arrays of booleans use 1 byte per element.
3 Comments
Tagir Valeev
I see no reason to call boolean the ugly sister. Internally bytes, shorts and chars are also often manipulated as 32-bit integers. User just should not care about these internals.
RealSkeptic
@TagirValeev The fact is that there is no language definition for the size of
boolean. All the rest of the types have that size defined in their wrapper classes (SIZE constant representing number of bits). You can write all types into a ByteBuffer - except boolean, etc.Tagir Valeev
@RealSkeptic, your comment sounds reasonable, but the "Internally it is manipulated as a 32 bit
int" statement in the answer is not.