There are two general kinds of numbers in Java and most other programming languages: binary integers and binary floating-point numbers (sometimes called real numbers). Although these numbers are stored in the computer as binary numbers, you will usually use decimal numbers in your Java source program, and the Java compiler will translate them to the correct binary form.
BigIntegerBigDecimalstrictfpshort) than
int?byte for integers that are in the range -128 to +127 because a
byte integer requires only 1/4 the memory that an int
does.
First, if you have only a small amount of data, as many programs do, the effect would be unmeasurable.
Second, because entire memory blocks are passed between the CPU and RAM there may not actually be any difference for small amounts of data! The exact way that memory is handled in the hardware is complex and often requires benchmarking (actual tests) to determine the speed of various options.
Large amounts of data are another matter, for example, when using arrays. If you're storing millions of numbers, their size has a definite effect on performance.
int and double are the types
that the Java compiler likes for integer and floating-point constants and expressions,
so you will find it much easier to use them. If you use other
sizes of numbers, you will have to write a lot of cast operators,
which is annoying and makes your code harder to read.
I used to choose the smallest type that would work for my data for efficiency reasons, but have
finally given up and just use int and double
because of the convenience - except for large amounts of data.