This document provides an overview of the steps to create a basic Java program. It discusses: 1) Using a text editor or IDE to write Java code in a .java file, compiling it to bytecode with the Java compiler, and running the bytecode with the Java interpreter. 2) The main() method signature including access modifiers, return type, name, and string array parameter. 3) Example code of a simple Java program in Notepad++ including the class name, main method, and use of System.out.println to print output.

1. INTRODUCTION
TO
JAVA PROGRAM

2. Java Program Development Steps
Text Editor /
IDE
File.java
(Text File)
Java
Compiler
Java
Interpreter
Result /
Output
File.class
(Bytecode)
O
n
c
e
Everytim
e

3. Oracle site

4. Oracle site
Java Virtual Machine
JRE
JDK

5. Oracle site
Java Virtual Machine
Runs the java bytecode
! Does not understand
java syntax and grammar
That is why we compile a
java program to
generate the bytecode
and understand the
bytecodes

6. Oracle site
JRE
Provides the JVM, libraries
to run java program
To execute application
Java Runtime Environment

7. Oracle site
JDK
Java Development Kit

8. WRITE YOUR
FIRST JAVA
PROGRAM IN
NOTEPAD++

9. Example of java program in notepad++
1st
key word
public

10. Example of java program in notepad++
2 access specifiers for Java classes
(not for inner classes)
1. Public
public class MyFirstClass
2. Default (don’t type anything)
class MyFirstClass

11. Example of java program in notepad++
2nd key word
Class
Name of the class
MyFirstClass
- use to create java classes
Declare all your classes with public access specifier

12. Example of java program in notepad++
Name of the
method
main
Name of the
variables
args

13. IDENTIFIERS in Java represent the following:
- Name of the class - Name of the method - Name of the variable
Identifiers are case sensitive.
Ex.
MyFirstClass is different from Myfirstclass
Examples of identifiers:
MyFirstClass, main, args, System (class name),
out (Reference Variable name)
println (method name)

14. Identifiers Naming Rules:
1. Name must begin with
a. A to Z (upper and lower case)
b. _ (underscore)
c. $ (dollar sign) or other currency symbol
Example of valid identifiers in java
EXAMCLASS
examCLASS
_Learners
_Course
$$Payment
$Fee

15. Identifiers Naming Rules:
2. After the first character, subsequent characters may use numbers from 0 - 9
Example of valid identifiers
A1Example
_123Test
$1Market

16. Identifiers Naming Rules:
3. Identifiers can’t use JAVA keywords
Example of invalid identifiers
public
class
void
static

17. Identifiers Naming Rules:
4. Identifiers can’t use following literals:
true
false
null

18. Keywords in Java
abstract continue for new switch
assert default goto package synchronized
boolean do if private this
break double implements protected throw
byte else import public throws
case enum instanceof return transient
catch extends int short try
char final interface static void
class finally long strictfp volatile
const float native super while
const & goto: are reserved even though they are not currently used
strictfp: added in JDK 1.2
assert: added in JDK 1.4
enum: added in JDK 5.0

19. WRITE YOUR
FIRST JAVA
PROGRAM IN
ECLIPSE

20. 2nd
line
Class definition in java must start with
{ opening curly bracket and
end with } closing curley bracket

21. Main method signatures are also valid:
static public void main(String[] args)[ ] { }
public static void main(String. . . args)[]{ }

22. 4 access specifiers can be applied to methods in java:
- Private
- Default (don’t specify anything
- Protected
- Public
But this special main method must be declared public only
3rd
line, 1st
word
public
Example of Access
specifier

23. 3rd
line, 2nd
word
static
Means main is shared
among all instances of
this class

24. 3rd
line, 3rd word
void
Means this method does not
written anything

25. 3rd
line, 4th
word
main
- this is the name of the method
- It an identifier

26. Method names in java are
followed by (.
If method takes no arguments
it should end with ).
Example:
Public void play()
But if method takes some arguments, add the arguments declarations and then add ).
Example:
Public void play(string sport)
Round brackets ( ) is used as part of method signature

27. args the name of the string
array parameter
String arrays [ ] accespts string arrays as a parameter
What are the arguments that we can pass inside the method?
{ opening bracket for the
main method

28. System.out.println
It prints text included/enclosed in double quote “ “
Displays the text in screen console
4th
line in eclipse program

29. 5th
line
Type sysout and press Ctrl + Space,
Auto-complete feature will write whole
System.out.println statement

30. To delete one line, place the cursor anywhere on the line and press Ctrl + D
To delete multiple lines, select multiple lines and press Ctrl + D

31. System.out.println () System.out.print(“ ");
Add a new line character takes
you to the next line
Keeps the cursor to the current line
Does not go to print to the next line

32. Semi colon ;
Semicolon is use to end the statement
You can use multiple semicolon
System.out.println("A");;;;
And it will not give you an error

33. Closing bracket of main method
Closing bracket of the class
Opening bracket of the
class
Opening bracket of the main