Transcript CIS 103 * Programmin Logic and Design

Java PAL
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Contains the development kit and the runtime
environment ( aka the Java Virtual Machine )
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Download Link:
http://java.sun.com/javase/downloads/index.jsp
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Installation
◦ Detailed instructions in the “Read This Before You Begin” section.
◦ Environment Variables
 Path
 Classpath
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Originally was to be called “Oak”
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Open Source Software ( free!! )
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Mainframes, minicomputers, servers, desktops,
notebooks, mobile devices, intelligent consumer
devices
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Windows, Linux, Unix, Macintosh, etc.
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Application Programming Interface
Class Library
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Packages
◦ Classes
 Methods
 Statements
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http://java.sun.com/javase/6/docs/api/
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Application
◦ A stand-alone program that runs on a computer.
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Applet
◦ An applet is a Java program that is executed and viewed in a
browser ( IE, Firefox, Navigator, etc. )
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Servlet
◦ A servlet is a Java program that runs on a Web server or
application server and provides server-side processing such as
accessing a database and e-commerce transactions.
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An object represents something in the real world, such
as a car, an employee, or an item in an inventory.
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Objects encapsulate attributes and behavior
 An attribute is a piece of information
 A behavior is an operation that may be used to manipulate the
value of an attribute
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Reusable software components that model real-world items
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Look all around you
 People, animals, plants, cars, etc.
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Attributes
 Size, shape, color, weight, etc.
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Behaviors
 Babies cry, crawl, sleep, etc.
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Even though Java is an object-oriented programming language, we will be
doing procedural programming using the language. In the CIS 182/282
courses you will explore object-oriented programming in Java.
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Java programs go through five phases:
◦ Edit
 Programmer writes program using an editor; stores program on disk with the
.java file name extension
◦ Compile
 Use javac (the Java compiler) to create bytecodes from source code program;
bytecodes stored in .class files
◦ Load
 Class loader reads bytecodes from .class files into memory
◦ Verify
 Bytecode verifier examines bytecodes to ensure that they are valid and do not
violate security restrictions
◦ Execute
 Java Virtual Machine (JVM) uses a combination of interpretation and just-in-time
compilation to translate bytecodes into machine language
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Classes are the fundamental unit of programming in
Java.
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Classes may be composed of:
◦ variables
◦ methods
corresponds to attributes
corresponds to behaviours
public class HelloWorld
{
public static void main(String args[])
{
System.out.println(“Hello World!”);
}
}
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class is:
method is:
header:
HelloWorld
main
public static void main(String args[])
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A translator translates a program (class) in one
language into another (often a machine language).
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A translator may be a:
◦ compiler
◦ interpreter
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translate only
translate and execute
Java uses both a compiler and an interpreter ( as do
applications in the Visual Studio environment )
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If you successfully compile a Java class, you produce a
class file.
This is a file with the same name as the program but
with a .class extension
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A Class file contains an intermediate language or
virtual machine language.
In Java this intermediate language is called bytecode.