Sách Java dành cho người mới học

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Java Programing

Language

SESSION 01 – Introduction to Java

• Choosing a development environment

• Writing a simple Java program

• Using the command-line tools

• Using Java NetBeans and Eclipse

– Originally called Oak

• Aimed at producing an operating environment for networked devices and embedded systems

– “Write once, run anywhere”

– Java is currently one of the most popular

programming language

The Java history timeline

Java Virtual Machine

• Java is both a compiled and an interpreted language

– Source code is compiled into Java bytecode

– bytecode is then interpreted by the J ava V irtual M achine

(JVM)

Java Virtual Machine (cont)

Java Code

Byte Code (.class)

JVM

Java language for Mobile application development

• Android (Java)

• Bada (C++)

• Black Berry (Java)

• iPhone, iPad (Objective-C)

Features of Java (cont)

• Simple :

– The syntax is mostly derived from C and C++

– Java has simplified C++ programming by remove some of complicated and difficult from C++

Features of Java (cont)

– Java’s support for Object-Orientation includes

inheritance, polymorphism, data access levels…– Not support multiple inheritance

Features of Java (cont)

• Platform-independent :

– Java was conceived with the concept of WORA:

“Write once, Run anywhere"

– Java code (.java) is compiled a byte code which is independent of the system

– Java byte code (.class) can run on any device

equipped with a Java Virtual Machine

Features of Java (cont)

• Robust : Java can be used to solve some very complex programming problems with the

Features of Java (cont)

• Secure :

– No pointers are forged

– No illegal object casts are performed

– There will be no operand stack overflows or underflows

– All parameters passed to functions are of the proper types

– Rules regarding private, protected, and public class membership are followed

Features of Java (cont)

• Multi-threaded:

– Multiple, synchronized threads is built directly into the

Java language and runtime environment

– Synchronized threads are useful in creating distributed, network-aware applications

Java compared with other languages

The popularity of Java

JDK and JRE

• The two principal products in the Java SE

platform: J ava Development Kit (JDK) and Java

Runtime Environment (JRE).

– The JRE provides the libraries, Java virtual machine,

and other components necessary for running applets

and applications written in the Java programming

language

– The JDK includes the JRE plus development tools such

as compilers and debuggers that are necessary or

useful for developing applets and applications

JDK and JRE

Download and install JDK

• The JDK is a development environment for building applications, applets, and components using the Java programming language.

• JDK can be download at http://www.oracle.com

• After downloading the JDK, follow the

platform-dependent installation directions At the time of this writing, they were available at

http://java.sun.com/javase/6/webnotes/install/ind ex.html.

Navigating the Java Directories

• The JDK has the directory structure shown

Setting the Execution Path

1 Click Start > Control Panel > System on

Windows XP or Start > Settings > Control

Panel > System (on Windows XP.)

2 Click Advanced > Environment Variables.

3 Add the location of bin folder of JDK

installation for PATH in User Variables and

System Variables A typical value for PATH is:

C:\Program Files\Java\jdk1.6.0_<version>\bin

Write a simple Java program

The first application will simply display the greeting "Hello world!"

• Step 1: Create a source file

public class Helloworld

• Step 2: Compile the source file into a class file

• Step 3: Run the program

Write a simple Java program

Write Java

code using

an editor

javac Helloworld.java

This creates a file of bytecode with a

.class extension

Using the Command-Line Tools

• Open a shell indow Go to directory where you

store your Helloworld.java and use javac

Using the Command-Line Tools

• The javac has a set of standard options:

Choosing a Development Environment

• NetBeans

• Jbuilder

• Eclipse

Using Java NetBeans

• Create a Java Project:

Using NetBeans

• Write a simple program:

Using NetBeans

• Program’s output in Console window:

• Java has three ways of marking comments:

– The most commonmethod is a //

– Use the /* and */ comment to block off a longer comment

• In this session, we learnt:

– History of Java

– Java Virtual Machine

– Types of Java programs

– Features of Java

– JRE and JDK

– Choosing a development environment – Writing a simple Java program

– Using the command-line tools

– Using Java NetBeans and Eclipse

– Basic of Java