1. Java

2. Java
In the Java programming language, all source code is first written in plain text files ending with the .java extension. – We will use DrJava text editor
Those source files are then compiled into .class files by the javac compiler. – It will compile to run on any machine.
A .class file contains bytecodes — the machine language of the Java Virtual Machine (Java VM).
The java launcher tool then runs your application with an instance of the Java Virtual Machine.

3. Java Virtual Machine
Because the Java VM is available on many different operating systems, the same .class files are capable of running on Microsoft Windows, the Solaris TM Operating System (Solaris OS), Linux, or Mac OS.

4. How to type the Java source code
Through an editor or IDE (Integrated Development Environment.)
Editor will generally highlight the Java syntax, indent for you, balance your parentheses and braces, and let you compile from within the editor.
IDEs have visual Java development tools, tight integration with the compiler or application server, and may include tools for debugging, refactoring, version control, and so forth.

5. What is DrJava?
DrJava is a free integrated development environment for doing Java programming
From Rice University
It is written in Java
It has several window panes in it
For creating programs (definitions pane)
For trying out Java code (interactions pane)
Listing of open files (files pane)
The pane that shows the code (on the right) is called the definitions pane.
The pane that allows you to type Java expressions and see the result is called the interactions pane.

6. Dr. Java Files Pane – List the open files in Dr. Java
Definitions pane – This is where you write your classes. Simply a text editor.
You compile all current files open in the files pane b y clicking on the compile all
Interactions Pane – You can type commands and it will execute but not save.

7. Java
A programming language specifies the words and symbols that we can use to write a program
Syntax: A programming language employs a set of rules that dictate how the words and symbols can be put together to form valid program statements
The Java programming language was created by Sun Microsystems, Inc.
It was introduced in 1995 and it's popularity has grown quickly since
It is an object-oriented language

8. Java Program Structure
In the Java programming language:
A program is made up of one or more classes Every program typed is in a class.
Class – blueprint for creating objects that have properties and methods.

9. The Java Application Programming Interface (API )
The API is a large collection of ready-made software components that provide many useful capabilities.
It is grouped into libraries of related classes and interfaces; these libraries are known as packages.

10. What Is a Package?
A package is a namespace that organizes a set of related classes and interfaces.
What is a class: A class is a generic template for a set of objects with similar features. All the GUI tools we will use are in a class called javax.swing.
The Java platform provides an enormous class library (a set of packages) suitable for use in your own applications. This library is known as the "Application Programming Interface",

11. Java Program Structure
// comments about the class
public class MyProgram { }
class header
class body
Comments can be placed almost anywhere

12. Java Program Structure
// comments about the class
public class MyProgram { }
// comments about the method
public static void main (String[] args) { }
method header
method body

13. Main method pubic static void main(String[]args) {
// program statements to print and execute }

14. Saving a File
You must save the java file with the same name as the class name.
It will save it with a .java extension.
The command to execute a compiled Java application in run.

15. Comments Comments in a program are called inline documentation
They should be included to explain the purpose of the program and describe processing steps
They do not affect how a program works
Java comments can take three forms:
// this is a single line comment
/* this is a multi-line comment that will
* take more than one line
**/
/** this is a javadoc comment. Used by
Programs for documentation. */

16. Identifiers
Identifiers are the words a programmer uses in a program. Can be reserved words Java has created or variables the programmer creates.
Rules for identifiers:
An identifier can be made up of letters, digits, the underscore character ( _ ), and the dollar sign
Identifiers cannot begin with a digit
Java is case sensitive - Total, total, and TOTAL are different identifiers
By convention, Java programmers use different case styles for different types of identifiers, such as
title case for class names - Lincoln
upper case for constants - MAXIMUM

17. Reserved Words The Java reserved words: abstract assert boolean break
byte
case
catch
char
class
const
continue
default do
double
else
enum
extends
false
final
finally
float
for
goto if
implements
import
instanceof
int
interface
long
native
new
null
package
private
protected
public
return
short
static
strictfp
super
switch
synchronized
this
throw
throws
transient
true
try
void
volatile
while

18. White Space Spaces, blank lines, and tabs are called white space
White space is used to separate words and symbols in a program
Extra white space is ignored
A valid Java program can be formatted in many ways
Programs should be formatted to enhance readability, using consistent indentation

19. There are 8 Primitive data types in Java.
Data type tells the kind of information that will be stored in memory.
TYPE
What it hold
RANGE
byte
Whole number
8 bits -128 to 127
short
16 bits
to 32767
int
whole numbers
32 bits -2 billion to 2 billion
long
64 bits -big to +big
float
Fractional number
32 bits -big to +big
double
fractional number
64 bits -1.7E+308 to 1.7E+308
char
‘A’
One character
16-bit
boolean
True or false value
Holds two values: {true, false}

20. Object
Turtle
Object 1
Turtle
Object 2
Objects are made from the class they belong to. You can create several objects from a class – like a cookie cutter.
Turtle: Class
JOptionPane jp = new JOptionPane();
Class
Variable name
New object created

21. Objects Objects - instance of a class. Objects have attribute or state
A state is a property or something the object knows about itself.
Turtle - size, color, name, age

22. Objects Objects have methods / Behavior / Actions
Things it knows how to do.
Turtle -
turn, turnRight, turnLeft, forward

23. Argument / Parameter
Parameter is extra information required to the object or method.
Turtle tom(130, earth);
They always appear in parenthesis.
Parameter – the information inside is called arguments
It is required so the Turtle will know where he is in the world and what world to be in.

24. Variables – stores value in a memory location
Programming uses variables. You need to learn this!
Declare is to tell what type of data the variable will hold and its name
int number;
double money;
boolean done;
You cannot use a variable until you declare the type
Initialize is to assign the variable a value using the = sign
int number = 37;
double money = 28.42;
boolean done = true;

25. Constants
Constants are variables that once assigned cannot change. They are identified by using the final and capitalizing the variable name.
final int SALARY;

26. Assignment Operator
The = sign is the assignment operator for variables.
int num = 2;
boolean done = true;
double average = 4.5;

27. Arithmetic Statements
45 / and 2 are called operand. er
Operators are:
+, - , * , / , %
Addition, substraction, multiplication, and modulus (remainder operator).

28. System Class Basic print statement in Java
System.out.println(“This will print”);
System is a class.
out is the object created from the System class
println is the method from the System class that allows it to print.
class
object
method
A period separates classes, objects and methods.

29. Print and Println Methods
//********************************************************************
// Countdown.java Author: Lewis/Loftus/Cocking //
// Demonstrates the difference between print and println.
public class Countdown { //
// Prints two lines of output representing a rocket countdown.
public static void main (String[] args)
System.out.print ("Three... ");
System.out.print ("Two... ");
System.out.print ("One... ");
System.out.print ("Zero... ");
System.out.println ("Liftoff!"); // appears on first output line
System.out.println ("Houston, we have a problem."); }
What will this program output look like
Three…Two…One…Zero…Liftoff!
Houston, we have a problem.

30. String Literals
The part inside the “ double quotes “ is called a String Literal.
Concatenation: Add one String to another using the + sign.
“ “ makes a space
System.out.println(“This is a String” + “ “ + “and this is another one.”);