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Data Types & Operators

Lecture from (Chapter 3,4)

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Review

An introduction to Object-oriented programming

Arithmetic OperatorsBitwise operatorsRelational OperatorsBoolean Logical OperatorAssignment Operator

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An introduction to Object Oriented Programming - http://java.sun.com/docs/books/tutorial/java/concepts/

Object-oriented Programming is the core of Java.

All java programms are object-oriented.We need to understand what an object is,

what a class is, how objects and classes are related, and how objects communicate by using messages.

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An overview of Object-oriented programming (1)

An object: An object is a software bundle of related variables and methods. Software objects are often used to model real-world objects you find in everyday life.

Messages: Software objects interact and communicate with each other using messages.

Class: A class is a prototype that defines the variables and the methods common to all objects of a certain kind.

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An overview of Object-oriented programming (2)

An inherientence: A class inherits state and behavior from its superclass. Inheritance provides a powerful and natural mechanism for organizing and structuring software programs.

An Interface: An interface is a contract in the form of a collection of method and constant declarations. When a class implements an interface, it promises to implement all of the methods declared in that interface.

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An object - We will introduce them one by one per week to build up your understanding

There are many examples of real-world objects. For example, our book, cat, pet etc.

These real-world objects share two characteristics, namely, : state and behavior.

For example, cats have state (color, hungry) and behavior (running , eating, sleeping).

Software objects are modeled following the real-world objects in that they too have state and behavior. A software object maintains its state in one or more variables

. A variable is an item of data named by an identifier. A software object implements its behavior with methods . A

method is a function (subroutine) associated with an object.

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Java Data Types

Primitive Data Types:boolean true or falsechar unicode! (16 bits)byte signed 8 bit integershort signed 16 bit integerint signed 32 bit integerlong signed 64 bit integerfloat,double IEEE 754 floating point

not an int!

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Arithmetic Operator – page 74

Operator Description+ addition- Subtraction* Multiplication/ Division% Modules++ Increment-- Decrement

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Example – addition and subtraction

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Example – multiplication and division

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Special operator

Expression Equivalent expression

a = a + 2; a +=2;

a = a – 4; a -= 4;

a = a*3; a *= 3;

a = a/4; a /=4;

a = a%2; a %=2;

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Example of special operator

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Increment and Decrement

Expression Equivalent expression

a = a + 1; ++a;

a = a – 1; --a;

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Bitwise Operators – page 81

Operator Description~ Bitwise unary NOT& Bitwise AND| Bitwise OR^ Bitwise exclusive OR>> Shift Right<< Shift LEFT>>> Shift Right with zero fill

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Operation - examples

Operator ExpressionAND 1 & 1 = 1; 1& 0 = 0OR 1 |1 = 1; 1| 0 = 1; 0|0 = 0~ 0 =~1; 1 =~0;^ 0^ 0 = 0; 1^1 = 0; 1^0 =1; 0^1 = 1>> 0x0010 = 0x0001 >>1<< 0x0001 = 0x0010 <<1>>> 0x1001 = 0x0100 >>>1

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AND Example – bits, 0x (hexadecimal)

1111 0010 (0xf2)1111 1110 (0xfe)---------------- (and) &1111 0010 (0xf2)

byte c = 0xf2;byte d = 0xfe;byte e = c & d; //e is 0xf2

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OR Example

1111 0010 (0xf2)1111 1110 (0xfe)--------------(or) |1111 1110 (0xfe)

Examplebyte c = 0xf2;byte d = 0xfe;byte e = c | d; //e is 0xfe

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One’s complement

1111 0010 (0xf2)

-------------- ~0000 1101 (0x0d)

Examplebyte c = 0xf2;byte e = ~c; //e is 0x0d

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EXCLUSIVE OR

1111 0010 (0xf2)1111 1110 (0xfe)-------------- (^) 0000 1100 (0x0c)

Examplebyte c = 0xf2;

byte d = 0xfe;byte e = c ^ d; //e is 0x0c

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Example

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Relational Operators

Operator Description

== Equal to

!= Not equal to

> Greater than

< Less than

>= Grater than or equal to

<= Less than or equal to

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Example

int a = 3;

int b = 4;

boolean c = (a>b); //c is false

boolean d = (a<b); //c is true

boolean e = (a==b); //c is false

boolean d = (a>=b); //c is false

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Example

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SHIFT >> (right) by one bit

1111 0010 (0xf2)>> 1 (shift right by one bit)---------------------

0111 0001 (0x79)

Examplebyte c = 0xf2;byte e = c >>1; //e is 0x79

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SHIFT >> by two bits

1111 0010 (0xf2)>> 2 (shift right by one bit)---------------------

0011 1100 (0x3c)

Examplebyte c = 0xf2;

byte e = c >>2; //e is 0x3c

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SHIFT << (left) by one bit

1111 0010 (0xf2)<< 1 (shift right by one bit)---------------------

1110 0100 (0xe4)

Examplebyte c = 0xf2;byte e = c <<1; //e is 0xe4

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SHIFT << by two bits

1111 0010 (0xf2)>> 2 (shift right by one bit)---------------------

1100 1000 (0xc8)

Examplebyte c = 0xf2;

byte e = c <<2; //e is 0xc8

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Results or bit operation (example)

(1 | 2) == 3 (1 | 3) == 3 (1 & 2) == 0 (1 & 3) == 1 (0 ^ 3) == 3 (1 ^ 3) == 2 (3 ^ 3) == 0 ~0 == -1 (signed) or 255 (unsigned)

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Example of shift

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Relational Operators

Operator Description

== Equal to

!= Not equal to

> Greater than

< Less than

>= Grater than or equal to

<= Less than or equal to

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Example

int a = 3;

int b = 4;

boolean c = (a>b); //c is false

boolean d = (a<b); //c is true

boolean e = (a==b); //c is false

boolean d = (a>=b); //c is false

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? operator

It is used to replace if-then-else statementExpression1 ? Expression2: Expression 3;If (expression1) is true, it will evaluate

Expression 2, else Expression 3

int i = 3;

int j = 4;

int k;

(i > j)? k = 10: k = 20; // (i > j) is false, k =20

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Summary

Object-oriented Programming is the core of Java. Each object consists of states and behaviour.

Arithmetic Operators -- +, - * /, ++, --, %Bitwise operators -- ~, ^, &, ^, >>, <<, >>>Relational operators -- ==, !=, >, < , >=, <=Boolean Logical Operator -- &. |, !, &=? Operator – Exp1? Exp2: Exp3