Java Reference
In-Depth Information
Gaining fluency . You will gain fluency in Java only by doing . As you read about expressions and
assignment, have your IDE (Interactive Development Environment) running on
your computer and practice typing in expressions and evaluating them. Experi-
ment, experiment! Often! For example, evaluate 5/2 and see what you get.
Type in Integer.MAX_VALUE and Integer.MAXVALUE + 2 and see what they
are. Try calling the mathematical functions with various arguments.
There is a major difference between conventional mathematical expressions
and Java expressions. In mathematics, an expression may have any value. It
might get big, but so what? But when using a programming language like Java,
the values of expressions are stored in a computer, which is a finite, physical
device. There is a tension among the sizes of the values of the expressions, the
space the values occupy, and the speed with which the values can be operated on.
Allowing expressions to have any value may cause values to take too much space
and operations to take too long.
Java uses the concept of a type to let you declare the range of values that you
want to work with and the operations you want to use. We define type :
A type is a set of values together with a set of operations on them.
In mathematics, we use the word integer for the type consisting of the inte-
ger literals {..., -3 , -2 , -1 , 0 , 1 , 2 , ...} together with these basic integer opera-
tions: negation, addition, subtraction, multiplication, and division.
1.1.1
Type int
In Java, type int consists of the integers in the range -2 31 ..2 31 -1 (by which
we mean the set of values { -2 31 , -2 31 + 1 , …, -1 , 0 , 1 , … 2 31 - 1 }). The
value 2 31 is 2 multiplied by itself 31 times, or 2147483648 .
The usual operations of type int are: negation, addition, subtraction, multi-
plication, division, and remainder. (Unary + is also available, but it is rarely
used.) All int operations have int results.
The smallest and largest values of type int are difficult to remember, so
Java gives you a notation for accessing them:
Lesson page
6-2
Activity
1-1.2
Integer.MIN_VALUE : smallest int value: -2147483648 .
Integer.MAX_VALUE : largest int type: 2147483647 .
To see this, type this expression into Java and see what value it gives you:
Integer.MAX_VALUE
Overflow
If a value of an int expression gets outside the range of type int , overflow
occurs. When overflow occurs, the value is changed back into one that is in the
range of type int . For example, 2147483647 + 2 in mathematics evaluates to
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