Programming in java

Lecture-3 (a)

Java Data TypeType Description

byte 8 bit signed integer

short 16 but signed integer

int 32 bit signed integer

long 64 bit signed integer

float 32 bit signed real number

double 64 bit signed real number

char 16 bit Unicode character (ASCII and beyond)

boolean 1 bit true or false value

String A sequence of characters between double quotes ("")

Boolean data type This data type can store only two values; true and

false. Declaring a boolean variable is the same as declaring any other primitive data type like int, float, char.

boolean response = false; //Valid boolean answer = true; //Valid boolean answer = 9943; //Invalid, boolean response = “false”; // Invalid,

This is return type for relational & conditional operators.

Comments // One line comment

/* multiple line Comment */

/*** These comment used in documentation *This is comment. *This is comment*/

What should be in comment? Author name Purpose of function

Default values for primitive members

When a primitive type data is a member of a class, it’s guaranteed to get a default value even if you don’t initialize it.

Not true for those local variables!! There will be compile

error if you use it without initialization

Primitive type Default

boolean false

char ‘\u0000’ (null)

byte (byte)0

short (short)0

int 0

long 0L

float 0.0f

double 0.0d

String (+) OperatorString Concatenation

"Now is " + "the time."

"Now is the time."

String (+) OperatorAutomatic Conversion to a String

If either expression_1If either expression_1 or expression_2 evaluatesto a string the other will be converted to a string if needed. The result will be their concatenation.

expression_1 + expression_2

String (+) OperatorAutomatic Conversion with Primitives

"The number is " + 4

"The number is " + "4"

"The number is 4"

Increment Operator • i + + first use the value of i and then increment

it by 1.

‘i + +’ equivalent to ‘i = (i)+1’. // postfix increment

• + + i first increment the value of i by 1 and then use it.

‘+ + i’ equivalent to ‘i = (i+1)’. // prefix increment

int i=2;

• System.out.print(“ i = ”+ i++);//print 2, then i becomes 3

• System.out.print(“ i = ”+ ++i);//add 1 to i, then print 4

Decrement Operator

• i - - first use the i ’s value and then decrement it by one

i - - equivalent to (i)-1. // postfix decrement

• - - i first decrement i ’s value by one and then use it.

- - i equivalent to (i-1). // prefix decrement

int i=5; System.out.print(“i = ” + i--);//print 5, then i

becomes 4 System.out.print(“i = ” + --i);//subtract 1 from i,

then print 3

Relational Operator a < b a less than b. (true/false)

a <= b a less than or equal b. (true/false)

a > b a greater than b. (true/false)

a >= b a greater than or equal to b. (true/false)

These operations always return a boolean value.

System.out.println(“23 is less than 65 ” +23<65); // true

System.out.println(“5 is greater than or equal to 25.00?” + 5>=25.00); // false

Equality Operator a = = b a equal to b. (true/false)

a ! = b a not equal to b. (true/false)

boolean equal = 12 = = 150; // false

boolean again_equal = ‘r’= = ‘r’); // true

boolean not_equal = 53!=90); // true

Logical (&&) Operator Examples

public class Example {public static void main(String[] args) {

boolean t = true;boolean f = false;

System.out.println("f && f " + (f && f));System.out.println("f && t " + (f && t));System.out.println("t && f " + (t && f));System.out.println("t && t " + (t && t));

}}

> java Example f && f false f && t false t && f false t && t true >

Logical (||) Operator Examples

public class Example {public static void main(String[] args) {

boolean t = true;boolean f = false;

System.out.println("f || f " + (f || f));System.out.println("f || t " + (f || t));System.out.println("t || f " + (t || f));System.out.println("t || t " + (t || t));

}}

> java Example f || f false f || t true t || f true t || t true >

Logical (!) Operator Examples

public class Example {public static void main(String[] args) {

boolean t = true;boolean f = false;

System.out.println("!f " + !f);System.out.println("!t " + !t);

}}

> java Example !f true !t false >

Logical Operators (Bit Level) & | ^ ~

int a = 10; // 00001010 = 10int b = 12; // 00001100 = 12

a 00000000000000000000000000001010 10b 00000000000000000000000000001100 12a & b 00000000000000000000000000001000 8

a 00000000000000000000000000001010 10b 00000000000000000000000000001100 12a | b 00000000000000000000000000001110 14

a 00000000000000000000000000001010 10b 00000000000000000000000000001100 12a ^ b 00000000000000000000000000000110 6

a 00000000000000000000000000001010 10~a 11111111111111111111111111110101 -11

&AND

|OR

^XOR

~NOT

Shift Operators (Bit Level) << >> >>>

• Shift Left << Fill with Zeros

• Shift Right >> Based on Sign

• Shift Right >>> Fill with Zeros

Shift Operators << >>int a = 3; // ...00000011 = 3int b = -4; // ...11111100 = -4

a 00000000000000000000000000000011 3a << 2 00000000000000000000000000001100 12

b 11111111111111111111111111111100 -4b << 2 11111111111111111111111111110000 -16

<<Left

>>Right

a 00000000000000000000000000000011 3a >> 2 00000000000000000000000000000000 0

b 11111111111111111111111111111100 -4b >> 2 11111111111111111111111111111111 -1

Shift Operator >>> int a = 3; // ...00000011 = 3int b = -4; // ...11111100 = -4

>>>Right 0

a 00000000000000000000000000000011 3a >>> 2 00000000000000000000000000000000 0

b 11111111111111111111111111111100 -4b >>> 2 00111111111111111111111111111111 +big

Shift Operator Examplespublic class Example {public static void main(String[] args) {

int a = 3; // ...00000011 = 3int b = -4; // ...11111100 = -4

System.out.println("a<<2 = " + (a<<2));

System.out.println("b<<2 = " + (b<<2));

System.out.println("a>>2 = " + (a>>2));

System.out.println("b>>2 = " + (b>>2));

System.out.println("a>>>2 = " + (a>>>2));

System.out.println("b>>>2 = " + (b>>>2));}

}

> java Example a<<2 = 12 b<<2 = -16 a>>2 = 0 b>>2 = -1 a>>>2 = 0 b>>>2 = 1073741823 >

Shift Operator >>> and Automatic Arithmetic Promotion

byte a = 3; // 00000011 = 3byte b = -4; // 11111100 = -4byte c;c = (byte) a >>> 2c = (byte) b >>> 2

>>>RightFill 0

a 00000011 3a >>> 2 00000000000000000000000000000000 0c = (byte) 00000000 0

b 11111100 -4b >>> 2 00111111111111111111111111111111 1073741823c = (byte) Much to big for byte 11111111 -1

Type Casting When a large data size variable is assigned to

small data size variable.

Declaration Size and Type Number

Range

byte b; // 8 bit integer -2-7 to +2+7-1

short s; // 16 bit integer -2-15 to +2+15-1

char c; // 16 bit Unicode 0 to +2+16

int i; // 32 bit integer -2-31 to +2+31-1

long l; // 64 bit integer -2-63 to +2+63-1

float f; // 32 bit floating point IEEE754 Standard

double d; // 64 bit floating point IEEE754 Standard

The Primitive Numbers

Casting the Primitives

b = (byte)s;b = (byte)c;b = (byte)i;b = (byte)l;b = (byte)f;b = (byte)d;

i = (int)b;i = (int)s;i = (int)c;i = (int)l;i = (int)f;i = (int)d;

l = (long)b;l = (long)s;l = (long)c;l = (long)i;l = (long)f;l = (long)d;

s = (short)b;s = (short)c;s = (short)i;s = (short)l;s = (short)f;s = (short)d;

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c = (char)b;c = (char)s;c = (char)i;c = (char)l;c = (char)f;c = (char)d;P

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f = (float)b;f = (float)s;f = (float)c;f = (float)i;f = (float)l;f = (float)d;

d = (double)b;d = (double)s;d = (double)c;d = (double)i;d = (double)l;d = (double)f;F

loat

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int

b = (byte)s;b = (byte)c;b = (byte)i;b = (byte)l;b = (byte)f;b = (byte)d;

i = b;i = s;i = c;i = (int)l;i = (int)f;i = (int)d;

l = b;l = s;l = c;l = i;l = (long)f;l = (long)d;

s = b;s = (short)c;s = (short)i;s = (short)l;s = (short)f;s = (short)d;

2's

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c = (char)b;c = (char)s;c = (char)i;c = (char)l;c = (char)f;c = (char)d;P

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f = b;f = s;f = c;f = i;f = l;f = (float)d;

d = b;d = s;d = c;d = i;d = l;d = f;F

loat

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Po

int

Acceptable Implicit Casts

char16 bit

double64 bit

float32 bit

long64 bit

int32 bit

short16 bit

byte8 bit

Illegal b = l;l = f;c = s;

OKl = b;i = c;f = l

char16 bit

double64 bit

float32 bit

long64 bit

int32 bit

short16 bit

byte8 bit

char16 bit

double64 bit

float32 bit

long64 bit

int32 bit

short16 bit

byte8 bit

Automatic Promotion with Arithmetic

Illegal Castss = s + b;s = s + s;

OKs = (short)(s + b);s = (short)(s + s);

Arithmetic is never donein 8 or 16 bit containers.

char16 bit

double64 bit

float32 bit

long64 bit

int32 bit

short16 bit

byte8 bit

Arithmetic Promotion with Mixed Primitives

Illegal Castsi = i + l;f = f + d;l = l + f;

OKi = (int)(i + l);d = (double)(f + d);l = (long)(l + f);

Arithmetic is donein the "widest" type.

Implicit Casts in Method Calls

char16 bit

double64 bit

float32 bit

long64 bit

int32 bit

short16 bit

byte8 bit

Illegal i = st.indexOf(f);

OKi = st.indexOf(c);i = st.indexOf(b);

For: String st; and,public int indexOf(int ch);

Program(find errors in following program)Class one { public static void main(String arp[]) { int i; Byte b=20; b=b+1; System.out.println(i); }}

Integer i is not initialised. Every local variable must be initialised.

b is automatically converted into integer data type and integer value can’t be assigned to byte variable

int a=12;float f=12.2f;double d=4.5;

double result = a * f + d ;

float type

a * f

= int * float + double

= float * float + double

= float + double

= double + double

= double