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The University of Akron
Summit College
2440: 160
Java Programming
Java Fundamentals
Instructor: Enoch E. Damson
Basic Java Programming Tips
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Java is case-sensitive
All Java programs must be stored in a file
with a .java extension
Comments are ignored by the compiler
A .java file may contain many classes, but
may only have one public class
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Basic Java Programming Tips…
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In a .java file with a public class, the class must
have the same name as the file
Every Java application program must have a
method named main
For every opening brace { or parenthesis (,
there must be a corresponding closing brace {
or parenthesis ) in Java
Java statements are terminated with semicolons
(;), except comments, method headers, or
braces
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The Java Application Programmer
Interface (API)
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A standard library of prewritten classes for
performing specific operations such as
standard input and output
The classes and their methods are
available to all Java programs
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Some classes/methods are available
automatically in all Java programs
Other classes/methods have to be
“imported” into Java programs
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Parts of a Java Application Program
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1.
2.
3.
4.
5.
6.
7.
8.
Below is a simple Java application
// This is a simple Java application program
public class Hello
{
public static void main(String[] args)
{
System.out.println(“Java Programming is fun…”);
}
}
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Parts of a Java Application
Program…
1.
The first line is a non-executable program
comment
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There are three comments used on Java and
they include:
// Line commend
 /* Paragraph comment */
 /** Javadoc generated paragraph comment */
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Parts of a Java Application
Program…
The second line defines a class named Hello
2.
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Everything used within a Java program must be
part of a class
A class can be defined using any name or identifier
as long as it satisfies the following criteria:
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A class name must begin with a letter of the alphabet
(Unicodes etc), an underscore, or a dollar sign
A class name can contain only letters, digits, underscores,
or dollar signs
A class name cannot be a Java programming reserved
word
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Parts of a Java Application
Program…
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In Java, standards are employed in the naming of classes to improve
readability
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This involves using uppercase letters to begin class names, and
emphasizing each word put together as a class name with an uppercase
letter
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It is recommended that established naming conventions be used in
order for other programmers to interpret and follow a program
Some valid, but unconventional class names include:
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E.g., Employee, UnderGradStudent, InventoryItem, Year2000
employee, Undergradstudent, Inventory_Item, YEAR2000
The reserved word public in public class Hello is an access
modifier that defines the circumstances under which a class can be
accessed
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public access is the most liberal type of access that allows other
programs to access a class (also used to define methods, and data
variables
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Parts of a Java Application
Program…
3.
Lines #3 and #8 indicate the beginning
and ending scopes of the class
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Contents of all classes are enclosed in curly
brackets { } which can contain any number
of data items and methods
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Parts of a Java Application
Program…
Line #4 has the method header, public static void main
4.
(String[] args)
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public – is the access modifier that allows public access to members
of the HelloWorld class
static – is also a modifier that represents uniqueness (a class
method) – only one main() method for the HelloWorld class will
ever be stored in the computer memory
void – means the main() method returns no value when it is called
main() – all Java applications must have a main() method because
that is the first method to be executed by a Java compiler, upon
execution of an application
(String[] args) – is the argument passed to the main() method
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String[] represents a Java class that can be used to represent a string of
characters or array of string objects
args is the identifier used to hold any strings passed to the main()
methods
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Parts of a Java Application
Program…
3.
Lines #5 and #7 indicate the beginning
and ending scopes of the main()
method
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Contents of all methods are enclosed in
curly brackets { }
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Parts of a Java Application
Program…
Within the statement in line #6 has the
statement:
6.
System.out.println(“Hello World”);
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System – a class defining the attributes of a collection of similar
System objects like out, in. and err
Within, System.out.println(“Hello World”);,
out – is an object that represents the screen and several
methods like println( ) are available with the out object
println() – is a method in Java programming that prints a
line of output on the screen, and positions the cursor on the
next line, and stands ready to accept any additional input
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print() also prints a line of output on the screen, but it positions the
cursor on the same line as the output, after printing the message
Method names are usually referenced followed by their
parenthesis in order to distinguish them from variable names
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Parts of a Java Application
Program…
The dots (.) in the statement System.out.println(“Hello World”);
are used to separate the names of the class, object, and
method
The text “Hello World” is a literal string of characters
that is meant to appear exactly as entered
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Any literal string in Java programming appears between double
quotation marks
The string “Hello World” appears within parenthesis
because the string is an argument to a method (in this
case the println() method)
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Arguments consist of information that a method requires for
performing its task
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Special Java Characters
Character
Name
Meaning
//
Double forward slash
Marks the beginning of a comment
()
Opening and closing parenthesis
Used in a method header
{}
Opening and closing braces
Encloses a group of statements
““
Double quotation marks
Encloses a string of characters
‘‘
Single quotation marks
Encloses a single character
;
Semicolon
Marks the end of a programming statement
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