Data Types

1
Data Types and Operators
2

• Java is a strongly types language
• all operations are types checked by the compiler
  for type compatibility
• illegal operations will not be compiled
• Java contains two sets of data types
• object-oriented data types
• non-object-oriented data types
• Java object- oriented data types are defined by
  classes.
• Discussion of these types will be done later in
  the course

3

• Primary data types
• Primary data types in Java are
• boolean Represents true or false value
• byte 8-bit integer
• char Character
• double Double-precision floating point
• float single-precision floating point
• int integer
• long Long integer
• short Short integer

4
Character variables can be handles like
integers class CharArithDemo public static void
main(String args) char ch ch
X System.out.println (ch contains
ch) ch // increment ch System.out.println
(ch is now ch) ch 90 // give ch the
value Z System.out.println( ch is now
ch)
Output Ch contains X Ch is now Y ch is now Z
A char can be incremented
A char can be assigned an integer value
Note that although char is not integer type, in
some case it can handled as integer
5

• Boolean type
• Boolean types represents true/false.
• true and false are reserved words in Java
• class BoolDemo
• public static void main(String args)
• boolean b
• b false
• System.out.println( b is b)
• b true
• System.out.println(b is b)
• // a boolean value can control the if statement
• b false
• if (b)
• System.out.println(This is not executed.)
• // outcome of a relational operator is a boolean
  value
• System.out.println(10 gt 9 is (10 gt 9) )

Output b is false b is true 10 gt 9 is true
6

• More on variables
• Initializing a variable
• One way to give a variable a value is through
  assignment statement
• For example,
• int count 10 // giving count initial value
  of 10
• char ch X // initializing ch to the
  value of X
• float f 1.3F // f is initialized with
  1.2
• You can also declare two or more variables of the
  same type using comma-separated list
• For example,
• int a, b 8, c 19, d // b and c are
  initialized

7

• Operator
• Java has four different classes of operator
  arithmetic, bitwise, relational, and logical
• Arithmetic operators include
• addition
• - subtraction
• multiplication
• / division
• module
• increment
• -- decrement
• , -, , /, work mainly the same as other
  languages.
• is the module operator. It works both for
  integer and floating-point numbers

8
class ModDemo public static void main(String
args) int iresult, irem double dresult,
drem iresult 10 / 3 irem 10 3 drem
10.0 3.0 dresult 10.0 / 3.0 System.out.prin
tln(Result and remainder of 10/3 iresult
irem) System.out.println(Result and
remainder of 10.0 /3.0 dresult
drem)

output Result and remainder of 10 / 3 3
1 Result and remainder of 10.0 / 3.0
3.3333333333333335 1.0
9

• Examples of increment and decrement
• X means X X 1
• X means X X 1
• Y X means Y X and X X1
• Y X means X X1 and Y X
• The same logic works for decrement (X-- )

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• Relational operators are
• ! gt lt lt gt
• Logical operators are
• And
• OR
• XOR
• ! Not
• The outcome of the relational operators is a
  boolean value
• The result of a logical operation is also of type
  boolean

11

• Suppose p and q are two boolean objects (literal,
  variable, expression), the following truth table
  holds
• p q pq pq !p !q
• ------------------------------------------------
  -
• T T T T F F
• T F F T F T
• F T F T T F
• F F F F T T
• For example, suppose c is a boolean variables and
  x10, y 20
• c ( x gt 15) (y 20)
• In this case since the first operand (xgt15) is
  false, the result of c is false no matter what
  the result of the second operand (y20) is.

12

• The Assignment operator
• The assignment operator is the single equal sign
  . The general format of assignment operator is
• var expression
• The type of expression should match the type of
  the variable
• It is also possible to create a chain of
  assignments
• For example
• int x, y, z
• x y z 100
• In this case, going from right to left, 100 is
  assigned to z which in turn z is assigned to y
  and the value of y is assigned to x
• Java also supports assignments for the following
  logical operators
• -
• For example, ab means a a b