after mid slide set 1

7/24/2019 After Mid Slide Set 1

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OBJECT ORIENTED PROGRAMM

(OOP)

15 TL-Sec I & IIEngr. Maria Shaikh

[email protected]


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Method Overriding

If subclass (child class) has the same method as declared in the

it is known as method overriding in java. In other words, If subclass provides the specific implementation

method that has been provided by one of its parent class, it is kmethod overriding.

When overriding a method, you might want to use the @Over

that instructs the compiler that you intend to override asuperclass .

Usage of Java Method Overriding Method overriding is used to provide specific implementation of

is already provided by its super class.

Method overriding is used for runtime polymorphism.Engr. Maria Shaikh


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Rules for Java Method Overrid

method must have same name as in the parent class

method must have same parameter as in the parent c

must be IS-A relationship (inheritance).

Engr. Maria Shaikh


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Implementation of Java MethoOverriding

class Animal {

public void move() {System.out.println("Animals can move");

}

}

class Dog extends Animal{

@Override

public void move() {

System.out.println("Dogs can walk and run");

}

}

public class TestDog {

public static void main(String[] args) {

Animal a = new Animal(); // Animal reference and object

Engr. Maria Shaikh


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Implementation of Java MethoOverriding

Dog b = new Dog(); // dog reference and object

a.move(); // runs the method in Animal cb.move();

}

}

Engr. Maria Shaikh


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Operators

Operators are special symbols that perform specific oone, two, or three operands, and then return a result.

The Simple Assignment Operator

One of the most common operators that you'll enco

simple assignment operator "=". You saw this operator in the Bicycle class; it assignsits right to the operand on its left:

int total = 0;

int speed = 0;

int gear = 1;Engr. Maria Shaikh


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The Arithmetic Operators

The Java programming language provides operators thaaddition, subtraction, multiplication, and division.

"%", which divides one operand by another and returnsremainder as its result.

Engr. Maria Shaikh

Operator Description

+ Additive operator (also used for Stconcatenation)

- Subtraction operator

* Multiplication operator

/ Division operator

% Remainder operator


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Implementation of Arithmetic Ope

class ArithmeticDemo {

public static void main (String[] args) {int result = 1 + 2;

System.out.println("1 + 2 = " + result); // result

int original_result = result;

result = result - 1;

System.out.println(original_result + " - 1 = " + result); // resu

original_result = result;

result = result * 2;

System.out.println(original_result + " * 2 = " + result); // re


result = result / 2;

System.out.println(original_result + " / 2 = " + result); // re

Engr. Maria Shaikh


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Implementation of Arithmetic Ope(cont.)


result = result + 8;

// result is now 10

System.out.println(original_result + " + 8 = " + result);


result = result % 7;

// result is now 3

System.out.println(original_result + " % 7 = " + result);

}

}

Engr. Maria Shaikh


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Output

Engr. Maria Shaikh


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+ Operator as a Concatenation Op The + operator can also be used for concatenating (joining) tw

together, as shown in the following ConcatDemo program:

class ConcatDemo {

public static void main(String[] args){

String firstString = "This is";

String secondString = " a concatenated string.";

String thirdString = firstString+secondString;

System.out.println(thirdString);

}

}

Engr. Maria Shaikh


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Output

Engr. Maria Shaikh


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The Unary Operators

The unary operators require only one operand; they perform v

operations such as incrementing/decrementing a value by onean expression, or inverting the value of a boolean.

Engr. Maria Shaikh

Operator Description

+Unary plus operator; indicates pos

(numbers are positive without this,

- Unary minus operator; negates an++ Increment operator; increments a v

-- Decrement operator; decrements a

!Logical complement operator; inve

boolean


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Implementation of Unary Opera

class UnaryDemo {

public static void main(String[] args) {int result = +1;

System.out.println(result); // result is now 1

result--;


result++;


result = -result;

System.out.println(result); // result is now -1

boolean success = false;

System.out.println(success); // false

System.out.println(!success); // true

}

} Engr. Maria Shaikh


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Output

Engr. Maria Shaikh


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Increment / Decrement with PrefPostfix

The increment/decrement operators can be applied before

after (postfix) the operand. The code result++; and ++result; will both end in result being

by one.

The only difference is that the prefix version (++result) evalincremented value, whereas the postfix version (result++)

the original value. If you are just performing a simple increment/decrement

really matter which version you choose. But if you use thispart of a larger expression, the one that you choose msignificant difference.

Engr. Maria Shaikh


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Implementation of Prefix

public class PreDemo {

public static void main(String[] args) {int a = 5;

int b = 3;

int d = a * ++b; // d is set to 20

System.out.println(d);

}

}

Engr. Maria Shaikh


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Implementation of Postfix

public class PostDemo {

public static void main(String[] args) {int a = 5;

int b = 3;

int c = a * b++; // c is set to 15

System.out.println(c);

}

)

Engr. Maria Shaikh


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Implementation of Prefix / Post

class PrePostDemo {

public static void main(String[] args){int i = 3;

i++;

System.out.println(i); // prints 4

++i;

// prints 5

System.out.println(i);

// prints 6

System.out.println(++i);

// prints 6

System.out.println(i++);

// prints 7

System.out.println(i);

}} Engr. Maria Shaikh


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Output

Engr. Maria Shaikh


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The Equality and Relational Opera

The equality and relational operators determine if one operan

than, less than, equal to, or not equal to another operand. Thethese operators will probably look familiar to you as well. Keepyou must use "==", not "=", when testing if two primitive values

== equal to

!= not equal to> greater than

>= greater than or equal to

< less than


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Implementation of Equality and RelaOperators

class ComparisonDemo {


int value1 = 1;

int value2 = 2;

if(value1 == value2)

System.out.println("value1 == value2");

if(value1 != value2)

System.out.println("value1 != value2");

if(value1 > value2)

System.out.println("value1 > value2");

if(value1 < value2)

System.out.println("value1 < value2");

if(value1


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Output

Engr. Maria Shaikh


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The Conditional Operators

The && and || operators perform Conditional-AND and Condit

operations on two boolean expressions. These operators exhibcircuiting" behavior, which means that the second operand is only if needed.

&& Conditional-AND

|| Conditional-OR

Engr. Maria Shaikh


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Implementation of Conditional Ope

class ConditionalDemo1 {


int value1 = 1;

int value2 = 2;

if((value1 == 1) && (value2 == 2))

System.out.println("value1 is 1 AND value2 is 2");

if((value1 == 1) || (value2 == 1))System.out.println("value1 is 1 OR value2 is 1");

}

}

Engr. Maria Shaikh


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Output

Engr. Maria Shaikh


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Bitwise and Bit Shift Operato

The Java programming language also provides operators that perform

bit shift operations on integral types. The operators discussed are leused. Therefore, their coverage is brief; the intent is to simply makethat these operators exist.

The unary bitwise complement operator "~" inverts a bit pattern; it cto any of the integral types, making every "0" a "1" and every "1" a "0a byte contains 8 bits; applying this operator to a value whose bit pat"00000000" would change its pattern to "11111111".

The signed left shift operator "" shifts a bit pattern to the right. The bit patby the left-hand operand, and the number of positions to shift by thoperand. The unsigned right shift operator ">>>" shifts a zero into thposition, while the leftmost position after ">>" depends on sign exten

Engr. Maria Shaikh


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Bitwise and Bit Shift Operators (

The bitwise & operator performs a bitwise AND oper

The bitwise ^ operator performs a bitwise exclusive operation.

The bitwise | operator performs a bitwise inclusive Ooperation.

Engr. Maria Shaikh


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Implementation of Complement Op

class ComplementlDemo1 {

public static void main(String[] args) {byte x = 3;

byte y = 5;

System.out.println(~x);

System.out.println(~y);

}

}

Engr. Maria Shaikh


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Implementation of bitwise AND op

class BitDemo {

public static void main(String[] args) {int bitmask = 0x000F;

int val = 0x2222;

// prints "2"

System.out.println(val & bitmask);

}

}

Engr. Maria Shaikh


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END OF SLIDES

Engr. Maria Shaikh

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