* : Java Glossary

*

In Java, multiplication is indicated by the * and *= operators. If you have an assembler background, Java multiplication may astonish you. When the CPU (Central Processing Unit) hardware multiplies two 32-bit quantities, usually it gets a 64-bit result. You might thus expect the result in Java of multiplying two 32-bit ints to be a 64-bit long. But it is not. It is truncated without overflow notification, to a 32-bit int.

There are other surprises. You might then expect byte * byte to be a byte, char * char to be a char, short * short to be a short, but they are not. All of them result in an int.

Further byte and short are sign extended to int before the multiply.

long * long gives a long, again truncating without overflow notification. long * int also gives a long.

Floating point, (float and double) works quite differently. float * float gives a float and double * double gives a double. double * float also gives a double. Floating point warns you when the multiply fails by giving NaN (Not A Number) results.

Learning More

Oracle’s JLS (Java Language Specification): expression evaluation order

+
++
-
--
/
assignment operator
division
floating point
modulus: the % operator
NaN
operator
precedence

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