Data Types & Operators
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Transcript of Data Types & Operators
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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