Integer numerical data types
The integer data types
• The integer data types use the binary number
system as encoding method
• There are a number of different integer types in Java
Integer operators
• Integer operators are arithmetic operators that manipulate
(operate on) integer values
• A integer operator only operates on integer values
• The result of an integer operator is always an integer value
Priority and associativity of the
integer arithmetic operators
The integer data types
• The computer can only perform operations on operands of
the same date type:
•
Correct
incorrect
Automatic conversions in Integer
arithmetic
• All values are converted to int type before an arithmetic
operation (+, −, *, /, %) in performed.
• If one of the values in an arithmetic operation is long,
then all values are converted to long type before
the arithmetic operation in performed.
Safe Conversions
• Safe conversions:
• Unsafe conversions:
Automatic type conversion in
the assignment operation
• The safe integer conversions are:
Summary of automatic conversion
rules (1)
• Integers:
When an arithmetic operation contains 2 integer values,
convert any lower precision integer type to int type
When an arithmetic operation contains a long value, convert
any lower precision integer type to long type
• Floating point numbers (float and double):
When an arithmetic operation contains 2 floating point
values, convert any lower precision float type to double type
Summary of automatic conversion
rules (2)
• When an arithmetic operation contains one floating point
value and one integer value:
convert the integer value to double
convert the lower precision float type to double type
Summary of automatic conversion
rules (3)
• If the range of values of type1 contains the range of values of type2,
then Java will perform an automatic promotion from type2 ⇒ type1 for
the assignment operation
Overflow
Reading integer input from the
keyboard
Numeric literals (1)
• A numeric literal is a constant value that appears in a Java
program.
• Every numerical literal (constant) has a data type
Numeric literals (2)
• Special tags that change the data type of a constant
• long tag:
The tag L or l after an integer literal will change the data
type of the literal to longExample:
12345L has the type long
• The float tag:
The tag F or f after a decimal literal will change the data
type of the literal to floatExample:
123.45f has the type float
Assigning integer constants
to byte and short variables (1)
• Strictly speaking, you need to use casting operators:
Assigning integer constants
to byte and short variables (2)
• If
an
integer
literal
(constant)
is
assigned
to
a byte typed or short typed variable,
the literal
(constant) is automatically converted into the appropriate
type if the constant is within the range of the data type of the variable.
• Example: The range of the byte type is −128 ... 127
The assignment expressions (1)
• Result of var = expr is equal to the value of expr
• In addition to updating the variable. the assignment
operator also returns a value
The assignment expressions (2)
• When there are multiple assignment operators in
an expression, the expression is evaluate from right to left
Assignment statements with the same
variable on the LHS and RHS
• The symbol "=" denotes an assignment operation:
1. The computer will first evaluate the RHS "x + 4.0":
RHS = x + 4.0 (x contains 1.0)
= 1.0 + 4.0
= 5.0
2. Then the result 5.0 is assigned to the receiving
variable x:
x = 5.0;
Therefore, after executing the statement "x = x + 4.0",
the variable x contains the value 5.0
Shorthand operators
• A shorthand operator is a shorter way to express something
that is already available in the Java programming language
The ++ and -- operators (1)
• Pre-operation: the ++ and -- operator appear before the
variable
• Post-operation: the ++ and -- operator appear after the
variable
• Both operations (++var and var++)
will increment the variable var by 1
• The only difference between ++var and var++ is:
the value that is returned by the expression.
The ++ and -- operators (2)
• The pre-operations ++a and --a will:
Apply the increment/decrement
operation before (pre) returning the value in the variable a
• The post-operations a++ and a-- will:
Apply the increment/decrement
operation after (pre) returning the value in the variable a
The ++ and -- operators (3)