Data types and Operators

Unit 1-Chapter 2
Data types and operators

contents
• Primitive types
• Literals
• Variables
• The scope and lifetime of variables
• Operators
• Type conversion in assignments
• Casting the incompatible types
• Operator precedence
• Expression

Primitive types
• Two categories of built-in data types:
– Object-oriented
– Non-object oriented
• There are 8 primitive data types offered by
java which are
• Boolean, byte, char, double, float, int,
long, short
• Java specifies a range and behavior for
each primitives type.

Integers
• Four types of integers : byte, short, int, long
Type Range Width
byte -128 to 127 8
short -32,768 to 32,767 16
int -2,147,483,648 to
2,147,483,647
32
long -9,223,372,036,854,775,808
to
9,223,372,036,854,775,807
64

class Inches{
public static void main(Strings args[]){
long ci;
long im;
im=5280*12;
ci=im*im*im;
System.out.println(“There are”+ci+” cubic inches in a
mile”);
}//end of the main
} //end of the Inches class
Output ??

Floating point types
• Two kinds of floating point
• float-single precision-32bits wide
• Double-double precision-64 bits wide
• sqrt( ) used to find a square root of a
number which returns a double value

Pythagoras theorem
class PthyThm{
public static void main(Strings args[]){
double x,y,z;
x=3;
y=4;
z=Math.sqrt(x*x+y*y);
System.out.println(“Hypotenuse is “+z);
}
}//end of PthyThm
Output ??

Charecters
• Unsigned 16 bit type having a range of 0
to 65,536
• Character variable can be assigned a
value by enclosing the character in a
single quotes
char ch;
ch= ‘X’;
System.out.println(“This is the value of
ch:”+ch);

• Arithmetic manipulations can be performed on the character
variable
class CharArithDemo{
public static void main(Strings args []){
char ch;
ch=‘X’;
Sytem.out.println(“The value of ch:”+ch);
ch++;
ch=90;
}
}
Output ??

Boolean type
• Represents true / false values
• Java uses keywords “true” and “false”
• A variable can be one of these type and
not both at the same time.
• Program to demonstrate boolean type

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);
if(b)
Sytem.out.println(“this is executed”);
b=false;
if(b)
System.out.println(“This is not executed..”);
System.out.println(“10>9 is “+ (10>9));
}
}
Output ??

Literals
• Literals refer to fixed values that are represented
in their human readable form
• Eg: 100 – constant
• Literals can be of any primitive types
• Integer literals are numbers without fractional
components
• Eg: 10, -100,450
• By default literals are of the type integer
• long int literal can be represented with a prefix L
• Eg: 12L

• Float literals can be specified by
mentioned f or F after the constant.
• Eg 10.95f
• Hexadecimal-base 16- 0 to 9 , A to F
which stands for 10-15
• Hexadecimal literal should begin with 0x
or 0X (zero follower by x or X)
• Hex=0xFF; //255 in decimal

• Octal-base 8- 0 to 7
• Oct=011; (begins with zero)
• Binary –base 2 – 0 or 1
• Precede the binary number with 0b or 0B
• 12 in binary 0b1100

Character escape sequences
• Also called as Backslash character constants
Escape sequence Description
’ Single quote
” Double quote
Backslash
r Carriage return
n New line
f Form feed
t Horizontal tab
b backspacem

class CharecterEx{
public static void main(String args[]){
char ch;
ch=‘t’;
System.out.println(“5”+ch+”00”);
ch=‘’’;
System.out.println(“5”+ch+”00”);
}
}
Output ??

String literals
• A string is a set of characters enclosed by
double quotes.
• “this is a test string”
class Strdemo{
System.out.println(“First linesecond line”);
System.out.println(“AtBtC”);
System.out.println(“DtEtF”);
}
}

variables
• Syntax  type variable_name;
• Type – data type that variable belongs to
• When you create a variable, you are
creating instance of its type.
• boolean variable cannot store a floating
point value
• int variable cannot store a character value
in it.

Initializing a variable
• type var=value;
• Value is the value that is stored in variable
named var when it is created.
• int count=10;
• char ch=‘x’;
• float f1=12.5;
• Same type variables can be declared and
assigned together in a single line
• For eg: int a,b=10,c=15 , d;

• Dynamic initialization
class Dynamic{
{
double radius=4,height=5;
double vol=3.14*radius*radius*height;
System.out.println(“Volume is :”+vol);
}
}
Output ??
Radius and height are initialized locally
Vol is initialised dynamically

The scope and lifetime of variables
• Java allows to declare variables in any
block.
• Block begins with a open and close curly
brace
• Block defines a scope
• Scope determines what objects are visible
to other parts of your program, also
lifetime of objects.

• Many languages defines scope in two categories
: global and local
• Java defines : by or within a method
• Scope defined by method begins with a opening
curly braces, parameters of the method are
included within method’s scope.
• Variables declared inside a scope are not visible
to code that is defined outside the scope.

• Scope provides foundation for
encapsulation.
• Scopes can be nested
• Outer scope , inner scope.
• Outer scope variables will be visible for
inner scope but vice versa is not true.

class ScopeDemo{
{
int x=10;
if(x ==10)
{
int y=20;
System.out.println(“x =”+x+”y= ”+y);
x=y*2;
}
y=100;
System.out.println(“x =“+x);
}
Output ??

• Variables are created when their scope is
entered and destroyed when their scope is
left.
• Values of the variables are lost as soon
they are out of the scope.
• Thu lifetime is confined to scope.
• Variable includes an intializer, that
variable will reinitialized each time the
block In which it is declared is entered.

class VarInitDemo{
int x;
for(x=0;x<3;x++)
{
int y=-1;
System.out.println(“y=“+y);
y=100;
System.out.println(“y=“+y);
}
}
}
Output ? ?

• No variable declared within an inner scope can have the same name as a
variable declared by enclosing scope.
class NestVar{
int i;
for(i=0;i<10;i++)
{
System.out.println(“Value of i =:”+i);
int i; // illegal – throws error
for(i=0;i<2;i++)
System.out.println(“Incorrect program!!”);
}
}
}
Output ??

Operators
• An operator is a symbol that tells the
computer to perform a specific
mathematical or logical manipulation.
• Four categories :
– Arithmetic
– Bitwise
– Relational
– Logical

Arithmetic operators
Operator Meaning
+ Addition
- Subtraction
* Multiplication
/ Division
% Modulus
++ Increment
-- decrement

class ModDemo{
int iresult,irem;
double dresult,drem;
iresult=10/3;
irem=10%3;
dresult=10.0/3.0;
drem=10.0%3.0;
System.out.println(“Result and remainder of 10/3 is :” +iresult+ “ “
+irem);
System.out.println(“Result and remainder of 10/3 is :” +dresult+ “ “
+drem);
}
}
Output ??

Increment ++ and Decrement --
• Increment operator adds 1 to its operand
and decrement operator subtracts 1
• x=x+1 is same as x++
• x=x-1 is same as x—
• Two forms for both , postfix and prefix
form
• Postfix x++ , x- -
• Prefix ++x,--x

• x=10;
• y=++x;
• Value of y =11 and x=10
• X=10;
• Y=X++;
• Here Y=10 and x=11;

Relational and Logical operators
• relational refers to the relationship that values can have with one another
• Logical refers to the ways in which true and false values can be connected
together.
• The outcome of both relational and logical operators is boolean value
Operator Meaning
== Equal to
!= Not Equal to
> Greater than
< Less than
>= Greater than or
equal to
<= Less than or
equal to
Operator Meaning
& AND
| OR
^ XOR
|| Short-circuit OR
&& Short-circuit AND
! NOT

p q p & q p | q p ^ q !p
T T T T F F
T F F T T F
F T F T T T
F F F F F T

class RelOps{
{
int i=10,j=11;
if(i<j)
System.out.println(“i < j”);
if(i<=j)
System.out.println(“i <= j”);
if(i!=j)
System.out.println(“i != j”);
if(i == j)
System.out.println(“this wont execute!”);
if(i >= j)
if(i > j)
}
}

class LogOps{
{
boolean b1=true,b2=false;
if(b1 & b2)
System.out.println(“This wont execute”);
if(!(b1 & b2))
System.out.println(“! (b1&b2) is true..”);
if( b1|b2)
System.out.println(“b1 | b2 is true”);
if(b1 ^ b2)
System.out.println(“ b1 ^ b2 is true..”);
}
}

Short-circuit logical operators
• In AND operation, if first operand is false , the result is
false, no need to evaluate the second operand.
• In OR operation, if first operand is true, the result is true,
no need of evaluating the second operand.
• By not evaluating second operand, time is saved and
more efficient code is produced.
• Short circuit AND / conditional AND operator ( && )
• Short circuit OR / conditional OR operator ( || )
• In short circuit operator, the second operand is evaluated
when it is necessary rest functionality is similar to & or |

class SCOpr{
int n=10,d=2,q;
if( d!=0 && (n%d) ==0)
System.out.println(d+ “is a factor of “+n);
d=0;
if( d!=0 && (n%d) ==0)
System.out.println(d+ “is a factor of “+n);
}
}

Assignment operator
• Assignment operator is a single equal to
sign
• var=expression
• int x,y,z;
• x=y=z=100;
• All the variables are initialized with the
value 100

Shorthand assignments
• x=x+10;
• x+=10;
• += operator pair tells the compiler to
assign the value of x plus 10
• y=y-10;
• y-=10;
• += -= *= /= %= &= |= ^=

Type conversion in assignments
• Assigning one type variable to another type
• int to float variable
int i=10;
float f;
f = i;
• Compatible types are implicitly type casted, it is
performed automatically, the value of i is converted to
float and then it is stored into f.
• boolean to int not compatible.

• Automatic conversion takes place only if
– The two types are compatible
– The destination is larger than the source type.
• byte to int , automatic conversion takes
place
• Eg: LtoD.java
• No automatic conversion from numeric
type to char or boolean.

Casting Incompatible types
• A cast is a instruction to the compiler to convert
one type into another.
• General form:
• (target-type)expresion
double x,y;
int z;
z=(int)(x/y);
• Why is parenthesis around x/y is necessary?

• During casting, i.e. narrowing conversion,
the value of the information might be lost.
• From long to short type.
• From float to int.

class CastDemo{
double x=10.0,y=3.0;
byte b;
int i;
char ch;
i=(int)(x/y);
System.out.println("Integer division of x/y is:"+i);
//range of byte is -128 to 127
i=100;
b=(byte)i;
System.out.println("Value of b:"+b);
i=257;
b=(byte)i; //out of range
System.out.println("Value of b:"+b);
b=88; //ascii for letter x
ch=(char)b;
System.out.println("ch:"+ch);
}
}

Shift operator
• Left shift <<
• Right shift >>
• Unsigned right shift >>>

Left shift
• Shifts all of the bits in a value to the left a
specified number of times.
• Multiply by 2
• Value << num
• Higher order bit is shifted out and zero is
brought in on the right.
• Incase of int, after 31 bit position, bits are
lost
• Incase of long, after 63.

class ByteShift{
{
byte a=64,b;
int i;
i=a<<2;
b=(byte)(a<<2);
System.out.println("Original value of a :"+a);
System.out.println("i and b :"+i+" " +b);
}
}

• 64– 0100 0000
• Shifting twice towards lefts
• 0100 0000 0 again
• 1 00 0000 00 which is 1 0000 0000 i.e
256 in integer

Right shift
• value>> num
• Divide by 2
• Shifts all the bits in a value to the right to
specified number of times and fills the
previous content present.
• Each time you shift a value to the right, it
divides that value by two and discards any
reminder generated.

class RightByteShift{
{
byte a=8;
int i;
i=a>>2;
System.out.println("value of a :"+a);
System.out.println("value of i:"+i);
}
}

• 8 in binary 0000 1000
• Right shift once 0000 0100 0 (4)
• Second time 0000 0010 0 (2)
• Serves as sign extension, -8<<1
• 1111 1000  -8
• 1111 1100  -4

Unsigned right shift >>>
• Sometimes keeping the sign shifted is
undesireble, if your shifting something that
does not represent a numeric value
• Pixel based values , graphics
• It shifts zero into higher order bits

class UnsignedRightShift{
{
int a=-1;
a=a>>24;
System.out.println("value of a after right shift:"+a);
a=a>>>24;
System.out.println("value of a after unsigned right
shift:"+a);
}
}

?: operator
• Exp1 ? Exp 2 : Exp 3
• Exp1 can be any expression that
evaluates to boolean
• If exp1 is true, exp2 will be executed
• If exp1 is false, exp3 will be executed.
• Both exp2 and exp3 should return the
same type, which cant be void.
• Ratio=denom==0 ? 0 : num/denom;

class Ternary{
int i,k;
i=10;
k=i <0 ? -i : i;
System.out.print("Absolute value of ");
System.out.println(i+" is "+k);
i=-10;
k=i <0 ? -i : i;
System.out.print("Absolute value of ");
System.out.println(i+" is "+k);
}
}

Operator precedence
Highest
(postfix)++ (postfix) - -
++(prefix) - -(prefix) ~ ! + (unary) - (unary) (type cast)
* / %
+ -
>> >>> <<
> >= < <= Instanceof
== !=
&
^
|
&&
||
?:
=
Lowest

( 1 + 2 ) % 3 * 4 + 5 * 6 / 7 * ( 8 % 9 ) + 10
3
42

Expressions
• Operators , variables and literals are
constitutes of expression.
• Type conversion in Expression:
• Within an expression it is possible to mix
to different types of data as long as they
are compatible with each other.
• Short and long can be mixed.
• It is accomplished using promotion rules.

• char, byte and short are converted to int.
• If one of the operand in the expression is
long, whole expression is promoted to
long.
• |||’y float, double
• Promotion rule apply on the values
operated upon when an expression is
evaluated.

• If the value of a variable is byte, it is
promoted to int inside the expression,
outside the expression it is still byte in
nature.
• The output of this type promotion might be
unexpected.
• Two variable which are byte in nature ,
they are promoted to int , the result
computed will be of int type.

class PromoDemo{
{
byte b;
int i;
b=10;
i=b*b;
b=10;
//b=(byte) (b*b);
b=(b*b);
System.out.println("i and b:"+i+"t"+b);
}
}

Spacing and parenthesis
• An expression may have a tab or spaces
to make it readable
• X=10/y*(127/x);
• X = 10 / y * (127/x);
• Both are same, but second expression is
much easier to read.
• Parenthesis increases precedence of the
operation contained with them.

• Use of additional parenthesis will not lead
to any kind of errors.
• X=y/3-34*temp+127;
• X= (y/3) – (34*temp) + 127;

Data types and Operators

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