The document provides an introduction to Java for beginners. It discusses Java's platform and virtual machine, programming environments and integrated development environments (IDEs) like NetBeans and Eclipse. It also covers Java fundamentals like data types, input/output, program structure, and common errors. The goal is to help new programmers get started with Java.
1. “Java” – for a beginner
By:
Biswadip Goswami
(c) Biswadip Goswami, biswadip_g@hotmail.com
2. 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
3. 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
4. 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
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
11. Using Comments
(c) Biswadip Goswami, biswadip_g@hotmail.com
12. 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
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
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
17. The Structure:
Any simple java program looks like
<access-specifier> class <class-name>
{
<access-specifier> static void main(varargs)
{
variables;
functions;
}
}
(c) Biswadip Goswami, biswadip_g@hotmail.com
18. 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
19. 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