Java for the Beginners

“Java” – for a beginner

By:
Biswadip Goswami

(c) Biswadip Goswami, biswadip_g@hotmail.com

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.


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


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

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.


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/]


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 !

The Programming Environment !


First Program !


Using Comments


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

• 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++);


Example


Input/Output
Lets check out an example for output –


• 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


The Structure:
Any simple java program looks like
<access-specifier> class <class-name>
{
<access-specifier> static void main(varargs)
{
variables;
functions;
}
}

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.

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

Java for the Beginners

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