Introduction to Java programming

Tuesday,September10,2013TOPSTechnologies-JavaTutorial
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TOPSTechnologies–JavaIntroductoryTutorial
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INTRODUCTION TO JAVA
TOPS Technologies – Java Introductory Tutorial
Module :1( theory)
http://www.tops-int.com/

TOPS Technologies – Java Introductory tutorial M1 3
WELCOME
• History
• First Java Application
• Data types
• Variables
• Strings
• Assignments
• Math, Boolean expressions
• Relational operations
• If statements
• System.exit

VERY BRIEF HISTORY
• Started in 1991 by SUN Microsystems
• Targeted at consumer electronics. Wanted reliable
programming language.
• Integrated into browsers
• Evolved into write once run anywhere, integrates
into Netscape
• General purpose libraries released

COURSE INFORMATION
 Textbook: Java in a Nutshell
Reading class 1
chapters 1,2

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BASIC DEFINITIONS
• Java is an object oriented language.
• Object
• Method
• Class
• Applications
• Applets
• Native classes
• Threads
• Exceptions
TOPS Technologies – Java Introductory tutorial M1

FIRST APPLICATION
/**
*Hello World, first application, only output.
*/
import java.io.*;
public class hello{
public static void main (String [] args) {
System.out.println(“Hello Worldn”);
} //end main
}//end class

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HOW TO GET IT RUNNING
• Text in hello.java file
• Why?
• To compile:
• javac hello.java
• To run:
• java hello

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NOTICE:
• Java is CASE SENSITIVE!!
• Whitespace is ignored by compiler
• Whitespace makes things easier to read…hence it
affects your grade 
• File name has to be the same as class name in
file.
• Need to import necessary class definitions

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VARIABLES
• Variables:
• Name
• Type
• Value
• Naming:
• May contain numbers,underscore,dollar sign, or
letters
• Can not start with number
• Can be any length
• Reserved keywords
• Case sensitive

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PRIMITIVE DATA TYPES
Byte 8 -27 27-1
Short 16 -215 215-1
Int 32 -231 231-1
Long 64
Float 32
Double 64
Boolean 1 0 1
Char 16

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ASSIGNMENT
• =
• Example:
• int n;
• n = 10;
• or
• int n = 10; //same

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STRINGS
• Not a primitive class, its actually something called a
wrapper class
• To find a built in class‟s method use API
documentation.
• String is a group of char‟s
• A character has single quotes
• char c = „h‟;
• A String has double quotes
• String s = “Hello World”;
• Method length
• int n = s.length;

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USING STRINGS
public class hello{
public static void main (String [] args) {
String s = “Hello Worldn”;
System.out.println(s); //output simple
string
} //end main
}//end class hello

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MATH
• Unary
• int x = -9;
• Regular math (+,-,*,/)
• int y = 3+x;
• % modulo operator

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INCREMENTING
• Increment and Decrement
• i++ equivalent to i = i + 1;
• Can also do ++i, which uses i before incrementing
it.
• Decrementing: i--;

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CASTING
int n = 40;
Wrong : byte b = n;
why??
Right: byte b = (byte) n;
Type casting converts to target type

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CASTING II
• Type char is stored as a number. The ASCII value
of the character.
• A declaration of :
• char c = „B‟;
stores the value 66 in location c
can use its value by casting to int
how??

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ASSIGNMENT
• +=
• -=
• *=
• /=
• %=

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BOOLEAN EXPRESSIONS
• boolean b
b will be either true (1) or false (0)
• Logical operations: !(not), && (and) || (or)
• boolean a,b;
a = true;
b = false;
System.out.println (“a && b is “ + (a && b));

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RELATIONAL OPERATORS
 == equality
 != inequality
 > greater than
 < less than
 >= greater than or equal to
 <= less than or equal to

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THE IF - BRANCHING STATEMENT
• if ( x < y) {
• x = y;
• }
• if ( x < y ) {
x = y;
}
else {
x = 88;
}

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IF/ELSE
• if (logic condition) {
something
}
else if (logic condition) {
something
}
else {
something else
}

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NESTED IF
if ( x < 0 ) {
System.out.println( “ x is negative “ );
}
else {
if ( x > 0 ) {
System.out.println ( “x is positive” );
}
//end if x > 0
else {
System.out.println ( “x is zero “ );
}
} //end else x >=0

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SWITCH/CASE
Switch(variable)
{
case(1): something;
break;
case(23): something;
break;
default: something;
}

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EXCEPTIONS
• Java exception object.
• java.io.Exception
most general one.
Some exception like in Throwable class define
methods to get the message.

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TRY….CATCH BLOCKS.
Try {
…….
}
catch ( IOException v) {
……….
}

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SYSTEM.OUT.PRINTLN
• println is a method in the Printstream class.
• Defined:
• public void println(String x)
can be any type of string or combination string using
addition to join parts.
Example:
println(“hello “ + “world “ + x);

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SYSTEM.EXIT()
• One method in java.lang.System
• Defined:
public static void exit ( int status)
• Terminates currently running Java VM
• Status is status code, non zero will usually
mean something abnormal.
• Used at end to indicate success, or in
middle to signal problems.

Introduction to Java programming

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