Download CPRG215 - Module 1 - Topic 1_v3_YD

CPRG 215
Introduction to
Object-Oriented Programming with Java
Module 1-Introduction to Java
Topic 1.1
Basics of Java
Produced by Harvey Peters, 2008
Copyright SAIT
Please read the following sections
in your textbook
Core Java, Volume I–Fundamentals, Eighth
Edition
(By Cay S. Horstmann & Gary Cornell)
•Chapter 1 - An Introduction to Java
•Java As a Programming Platform
•The Java "White Paper" Buzzwords
•Java Applets and the Internet
•A Short History of Java
•Common Misconceptions about Java
CPRG 215 Module 1.2- Getting the Tools and Setting Up the Development Machine
Copyright SAIT
What is Java?
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Object-oriented
Distributed
Portable/Architecture-neutral
Reliable
Secure
Multi-threaded
Dynamic
– no link step - run-time flexibility
CPRG 215 Module 1.1- Basics of Java
Copyright SAIT
Topic 1.1.1
What is Java?
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Programming Language
Development Environment
Application Environment
Deployment Environment
CPRG 215 Module 1.1- Basics of Java
Copyright SAIT
Topic 1.1.1
Characteristics of Java
• Java is compiled to “bytecode”
– Not binary like most compiled languages
• Bytecode is interpreted by the Java Virtual
Machine (JVM)
• Performance
– JVM is optimized -- speed approaching that of C++
• Optimization
– JVM optimized for hardware and operating system
• Portability
– Java programs run on JVM, isolated from
hardware & operating system – platform
independent
Topic 1.1.2
CPRG 215 Module 1.1- Basics of Java
Copyright SAIT
Java Compared to C++
• C++
– Performance
• Used when high speed is required
– Control
• Tight control over memory usage
• Java
– Portability
• Can run on any JVM (some version issues though)
– Reliability
• Exception handling reduces crashes
– Security
• Built-in security eliminates problems of other
languages
CPRG 215 Module 1.1- Basics of Java
Copyright SAIT
Topic 1.1.3
JVM
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Java Program
JVM
O/S
Java Virtual Machine (JVM)
Layer between Java code and hardware
Bytecode interpreter
Can be software or can be built-in to the
hardware
• Part of the development tool or the Web
browser
• Buffer between program and platform
– Platform independence
Hardware
CPRG 215 Module 1.1- Basics of Java
Copyright SAIT
Topic 1.1.4
JVM
• Bytecode
– machine-code instructions
– checked by compiler
– must be able to run on any Java compliant
interpreter
CPRG 215 Module 1.1- Basics of Java
Copyright SAIT
Topic 1.1.4
JVM
• Garbage collection
– memory allocated by assigning a pointer to the
memory address
– most languages require program to clean-up
and free its memory when complete
• leads to memory leaks if not handled
correctly
– Java automatically manages this
CPRG 215 Module 1.1- Basics of Java
Copyright SAIT
Topic 1.1.4
JVM
• Security
– Security Manager built into JVM
– Provides cryptography, authentication &
authorization, public key architecture
– “customizable sandbox”
• Security policy can be customized for finegrained control
– Language security
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Strong data typing
Automatic memory management
Bytecode verification
Secure class loading
– Prevents memory violations, buffer overflows,
and more
CPRG 215 Module 1.1- Basics of Java
Copyright SAIT
Topic 1.1.4