Since there’s little we can do with numeric
values alone, Java provides us with the ability to define and work with
variables. As variables are representations
of values, we expect to be able to write more complex programs using
variables, and indeed this is true. In
Java, variables could refer to numeric or non-numeric values. Our attention will first be directed
towards variables that hold numeric values.
These can naturally be thought of as falling in one of two groups: the
integers (whole numbers) or real numbers (those with decimals). We’ll ignore complex numbers. Java defines data types to
make the distinction between whole numbers and decimals. In fact, each variable must have a type in
Java. There are several data types in
Java to represent numeric values (many more than we’d expect), but for now
we’re going to consider only the four most common ones: Type What it represents int A whole number, positive or negative
approximately in the range -2.1E9 and +2.1E9 (if scientific notation escapes
you, 2.1E9 is 2.1B) long A whole number, positive or negative
approximately in the range -9.2E18 and +9.2E18. float A decimal number approximately in the range
-3.4E38 to +3.4E38 with 6 or 7 digits of precision double A decimal number approximately in the range -1E308
to +1E308 with 14 or 15 digits of precision |