“Java” – for a beginner : “Java” – for a beginner By:
Biswadip Goswami (c) Biswadip Goswami, biswadip_g@hotmail.com
What are we going to venture ! : What are we going to venture ! The Platform.
Java Virtual Machine.
The Programming Environment.
Some fundamentals (datatypes etc.).
Structure of a Java Program.
Mistakes we make while writing the code. (c) Biswadip Goswami, biswadip_g@hotmail.com
The platform : The platform Java is a whole platform !
Huge library
Lots of reusable code
Execution environment providing services as
Security
Portability
Automatic garbage collection and more (c) Biswadip Goswami, biswadip_g@hotmail.com
The Virtual Machine : The Virtual Machine JVM or Java Virtual Machine.
Platform independent execution environment
Convert ByteCode to machine code
Mimics a real Java processor
The ByteCode is executed regardless of the Operating System
A ByteCode stream: 03 3b
The mnemonics
iconst_0 // 03
istore_0 // 3b (c) Biswadip Goswami, biswadip_g@hotmail.com
Slide 5 : JVM and Garbage Collection:
JVM stores all objects by the java applications and Garbage Collection is a process of automatically freeing those objects which are not referenced by the program any more.
Garbage collector also stops heap fragmentation. (c) Biswadip Goswami, biswadip_g@hotmail.com
Some IDEs Available: : Some IDEs Available: NetBeans [http://www.netbeans.org]
Eclipse [http://www.eclipse.org]
JBuilder 7 [http://www.borland.com/jbuilder]
Oracle9i JDeveloper [http://www.oracle.com/ip/develop/ids/] (c) Biswadip Goswami, biswadip_g@hotmail.com
JARGONS ! : JARGONS ! JDK – Java development kit
JRE – Java runtime environment
SE – Standard Edition
EE – Enterprise edition
ME – Micro edition
J2 – Java 2
SDK – Software development kit
Netbeans – there is no acronym sorry ! (c) Biswadip Goswami, biswadip_g@hotmail.com
The Programming Environment ! : The Programming Environment ! (c) Biswadip Goswami, biswadip_g@hotmail.com
First Program ! : First Program ! (c) Biswadip Goswami, biswadip_g@hotmail.com
Slide 10 : (c) Biswadip Goswami, biswadip_g@hotmail.com
Using Comments : Using Comments (c) Biswadip Goswami, biswadip_g@hotmail.com
Data Types : Data Types Java is a strongly typed language
Eight primitive types in Java
Integer types
int (4bytes)
Short (2bytes)
Long (8bytes)
Byte (1byte)
Floating point type
Float (4bytes)
Double (8bytes) (c) Biswadip Goswami, biswadip_g@hotmail.com
Slide 13 : Char type – used to describe individual characters. E.g. - \b (backspace), \t (tab)
Boolean type – it has two values ‘true’ and ‘false’.
After declaring a variable, it must be explicitly initialized. E.g. int days=30;
In java declaration can be done anywhere in the code. E.g. for(int x;x<=10;x++); (c) Biswadip Goswami, biswadip_g@hotmail.com
Example : Example (c) Biswadip Goswami, biswadip_g@hotmail.com
Input/Output : Input/Output Lets check out an example for output – (c) Biswadip Goswami, biswadip_g@hotmail.com
Slide 16 : Console input and output in Java.
Standard output stream (System.out.println)
Standard input stream (System.in)
Methods of Scanner class reads inputs.
Scanner(System.in)
nextLine method – input with space
next method – input single string (c) Biswadip Goswami, biswadip_g@hotmail.com
The Structure: : The Structure: Any simple java program looks like
class
{
static void main(varargs)
{
variables;
functions;
}
} (c) Biswadip Goswami, biswadip_g@hotmail.com
Troubleshooting: : Troubleshooting: Check for upper and lower case of class name and .java program name.
Bad command or file name - check for installation
Cannot read: xyz.java – check for the file in the current directory
Error about new language construct – check for the latest version of JDK
Cannot find the symbol – check for the name/keywork/identifier
Using an IDE generally saves you from setting of the CLASSPath. (c) Biswadip Goswami, biswadip_g@hotmail.com
Thank you ! : Thank you ! For assistance with your ASP.Net or JAVA requirements contact:
Biswadip Goswami
Primary e-mail: biswadip_g@hotmail.com
Alt e-mail: biswadip@cognobytes.com
Webpage: http://people.cognobytes.com/biswadip
Skype me at biswadip.g (c) Biswadip Goswami, biswadip_g@hotmail.com