JAVA Variables and Operators

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Variables & Operators
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2. Variables
 Variable stores human data
like numbers and alphabets.
 Data type will decide what
values will be stored in
variables.
 You can say data type will
define the structure of your
data.
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3. Variables and Data Types
Decimal values will be stored in float and
double data type.
Non-decimals values will be stored in int,
long, byte, and short data types.
Character will be stored in char data type.
True/False will be stored in boolean data type.
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Data Types
Data types are divided into two categories.
Primitive Data Types
o byte, short, int, long, float, double,
boolean, char.
o It occupies number of bytes as per data type.
o It stores values.
Reference Data Types
o It stores memory address of a value.
o It occupies 2 bytes to store a reference (memory
address).
o Strings, Objects, Arrays are reference data types.

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Primitive Data Types
int
long
byte
short
float
double
1
2
4
8
4
8
-128, +127
-9.223E18, +9.223E18
-32768, +32767
-2147483648, +2147483647
+3.4 E+38
+1.7 E+308
Type Size Byte Range
char 2 0, 65535
boolean 1 true, false
0
0
0
0
0
0
0
false
Default

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Declare Variable
int total;
total = 5+6;
short srt;
srt = 3;
char ch;
ch =‘A’ ;
4 Bytes
Stack Memory1001
total 1001
11
2 Bytes
1011
3
srt 1011
2 Bytes
1010
A
ch 1010

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Declare Object
 int total;
 total = 5+6;
 String str;
 str = “sunRays”;
o or
 str = new
String(“sunRays”);
4 Bytes
Stack Memory
1001
total 1001
11
2 Bytes
1011
1010
str 1011
14 Bytes
1010
SUNRAYS

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Declare Variable – Primitive Data
 int total;
 total = 5+6;
 int newTotal;
 newTotal = total ;
 newTotal =
newTotal+3 ;
4 Bytes
Stack Memory1001
total 1001
11
4 Bytes
1011
newTotal 1011
1114

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Declare Object - Copy reference
 String str;
 str = “sunRays”
 Or
 str = new
String(“sunRays”)
 String newStr;
 newStr = str;
Stack Memory
2 Bytes
1011
1010
str 1011
14 Bytes
1010
SUNRAYS
2 Bytes
1110
1010
newStr 1110

10. Java Identifier
It is a name of:
o Variable
o Method
o Class
o Interface
o Package
Used to identify a variable, method and
class in its scope.
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Java Identifier Rules
 Name of an Identifier follows certain rules. Here are key
rules:
o The first character must be a non-digit character from the Unicode
standard String firstName;
o Subsequent characters may include digits int total123 ;
o Java is case sensitive that means Character Case is significant
• int count =0 ; Count = 1 ; are two different variables
o Avoid using underscore (_) and $ for the first character.
o User-defined identifiers can not duplicate Java keywords.

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What’s an operator?
Operators are tokens that trigger some
computation when applied to variables and
other objects.
It can be categorized into:
o Arithmetic
o logical
o bit-level and
o Class access operators.

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Java operators
()
++
--
!
~
instance of
*
/
%
+
-
<<
>>
>>>
<
>
<=
>=
==
!=
&
^
|
&&
||
?:
=
op=

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Operator Precedence
int a = 2+ 4 + 8;
int a = 2+ 4 * 8;
int a = b = c = 5;

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Operator Precedence
Operators Precedence
postfix expr++ expr--
unary ++expr --expr +expr -expr ~ !
multiplicative * / %
additive + -
shift << >> >>>
relational < > <= >= instanceof
equality == !=
bitwise AND &
bitwise exclusive OR ^
bitwise inclusive OR |
logical AND &&
logical OR ||
conditional ? :
assignment = += -= *= /= %= &= ^= |= <<= >>= >>>=

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Precedence
Operators have the precedence. Higher
precedence operator will be evaluated before the
lower precedence operator.
o int data = a * b + c ;
since * (multiply) has higher precedence than +
(plus) so a & b will be multiplied first then result will
be added to c.
Expression is equivalent to
o int data = (a * b) + c ;

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Unary operators
()()
++++
Group expression
Unary plus
Unary minus----

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Unary operators
~~~~
!!!!
++++++++
--------
Bitwise complement
Logical negation
Pre- or Post-increment
Pre- or Post-decrement

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Unary operators
i = 0;
count = 2 + i++;
i = 0;
count = 2 + i++;
ii
countcount
11
22
i = 0;
count = 2 + ++i;
i = 0;
count = 2 + ++i;
ii
countcount
11
33

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Binary operators
 yyyy
OperandOperand
xxxx
OperandOperand
OperatorOperator

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Binary operators
++
--
**
//
Plus
Minus
Multiply
Divide
Remainder
Additive & Multiplicative
%%

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Binary operators
== AssignmentAssignment
 Assignment is an binary operator in Java.
 The left-hand operand of an assignment must be an
LVALUE.
 An LVALUE is an expression that refers to a region of
memory.
o Names of variables are LVALUES.
o Names of functions and arrays are NOT LVALUES.

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Binary operators
class ExampleAssignment {
public static void main(String[] args) {
int result, val_1, val_2;
result = (val_1 = 1) + (val_2 = 2);
System.out.println("val_1 = "+val_1);
System.out.println("val_2 = "+val_2);
System.out.println("result = "+result);
}
}
class ExampleAssignment {
public static void main(String[] args) {
int result, val_1, val_2;
result = (val_1 = 1) + (val_2 = 2);
System.out.println("val_1 = "+val_1);
System.out.println("val_2 = "+val_2);
System.out.println("result = "+result);
}
}
val_1 = 1
val_2 = 2
result = 3
val_1 = 1
val_2 = 2
result = 3

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Binary operators
Expressions involving only integers are
evaluated using integer arithmetic.
float result;
int i,j;
i=25; j=10;
result = i/j;
float result;
int i,j;
i=25; j=10;
result = i/j;
resultresult 2.02.0

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Binary operators
Expressions involving only integers are
evaluated using integer arithmetic.
float result;
int i,j;
i=25; j=10;
result = (float) i/j;
float result;
int i,j;
i=25; j=10;
result = (float) i/j;
resultresult 2.52.5

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Binary operators
+=+=
-=-=
*=*=
/=/=
Assign sum
Assign difference
Assign product
Assign quotient
Assign remainder%=%=

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Binary operators
Compound operators provide a
convenient shorthand.
int i;
i = i + 5;
i += 5;
int i;
i = i + 5;
i += 5;

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Binary operators
<<
>>
<=<=
>=>=
Less than
Greater than
Less than or equal to
Greater than or equal to
Equal to
Not equal to
Relational
== ==
!=!=

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Binary operators
&&&&
||||
Logical AND
Logical OR
Logical
Expressions connected by && and || are
evaluated from left to right.

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Binary operators
Expressions connected by && and || are
evaluated from left to right.
class ExampleAndOr {
public static void main(String[] args) {
int i=0;
System.out.println("Test:" + ((2<3) || (0<i++)));
System.out.println("I:" + i);
}
}
class ExampleAndOr {
public static void main(String[] args) {
int i=0;
System.out.println("Test:" + ((2<3) || (0<i++)));
System.out.println("I:" + i);
}
}
Test:true
I:0
Test:true
I:0
This never gets
evaluated!
This never gets
evaluated!

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Bitwise Binary operators
<<
>>
&
^
Shift left
Shift right
Bitwise AND
Bitwise XOR
Bitwise OR
unary bitwise complement
unsigned right shift
|
~
>>>
These operators are less commonly used.

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Unary bitwise complement
1 1 11 0 101
~
1 Byte
0 0 00 1 010
byte a = 10;
byte b = ~a;

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Left Shift <<
1 1 01 0 101
<<
1 Byte
1 0 10 0 001
byte a = 10;
b = a<<2;
1
1

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Right Shift >>
1 1 01 0 101
>>
1 Byte
1 0 10 1 100
byte a = 10;
b = a>>2;
1
0

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Unsigned Right Shift >>>
1 1 01 0 101
>>>
1 Byte
0 0 11 1 100
byte a = 10;
b = a>>>2;
1
0

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And bitwise &
1 1 01 0 101
&
1 Byte
0 0 11 1 100
byte a = 10;
b = 20;
c = a & b;
0 0 01 0 100

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OR bitwise |
1 1 01 0 101
|
1 Byte
0 0 11 1 100
byte a = 10;
b = 20;
c = a | b;
1 1 11 1 101

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XOR bitwise ^
1 1 01 0 101
^
1 Byte
0 0 11 1 100
byte a = 10;
b = 20;
c = a ^ b;
1 1 10 1 001

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Ternary operators
a?x:ya?x:y
“if a then x, else y”
Conditional
result = (x<y) ? x : y;result = (x<y) ? x : y;

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Multiple Assignments
int a = b = c = 10;

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Exercise
What is the result of
 int i = 0 ;
 System.out.println(++i + ++i + ++i + ++i + ++i + ++i);
 System.out.println(“” + ++i + ++i + ++i + ++i + ++i + ++i);

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Type Conversion

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Small to Big data type
Will be done automatically.
oint i = 5;
odouble d = i;
oshort s = 10;
oint i = s;
olong l = i;

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Big to Small data type
When precision or data loss likely to happen
then type casting is required.
o double d = 5;
o int i = (int)d;
o short s = (short)i;
o int i = 10;
o float f = (float)i;

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Mixing operators
class MixOperator {
public static void main(String[] args) {
char cv;
int iv1 = 64;
cv = (char) iv1;
System.out.println("cv:" + cv);
System.out.println("iv1:" + iv1);
}
}
cv:@
iv1:64

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Mixing operators
class MixOperator1 {
public static void main(String[] args) {
double fv1, fv2;
int iv1 = 123;
fv1 = iv1/50;
fv2 = iv1/50.0;
System.out.println("fv1:" + fv1);
System.out.println("fv2:" + fv2);
}
}
fv1:2.0
fv2:2.46
fv1:2.0
fv2:2.46

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String to Other data type
String str = “5.5” ;
int i = Integer.parseInt(str);
double d = Double.parseDouble(str);
float f = Float.parseFloat(str);
long l = Long.parseLong(str);
String bStr = “true”;
boolean b = Boolean.parseBoolean(bStr);

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Other data type to String
String str = String.valueOf(5);
String str = String.valueOf(5.5);
String str = String.valueOf(true);
String str = String.valueOf(5L);
String str = String.valueOf(5.5D);

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This presentation is available for free to computer
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We are grateful to owners of these URLs and
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