slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Java 程序设计 PowerPoint Presentation
Download Presentation
Java 程序设计

Loading in 2 Seconds...

play fullscreen
1 / 27

Java 程序设计 - PowerPoint PPT Presentation


  • 308 Views
  • Uploaded on

Java 程序设计. Java Programming Fall, 2013. Contents for Today. Java Program Structure How to Compile a Java Program How to Run a Java Program Environment Variables Java Commands. Example 2.1:. /*****First Java Program: HelloWorld.java *****/ //* Author: Mary public class HelloWorld {

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Java 程序设计' - olympe


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Java 程序设计

Java Programming

Fall, 2013

contents for today
Contents for Today
  • Java Program Structure
    • How to Compile a Java Program
    • How to Run a Java Program
  • Environment Variables
  • Java Commands
example 2 1
Example 2.1:

/*****First Java Program: HelloWorld.java *****/

//* Author: Mary

public classHelloWorld

{

public static void main( String[ ] args )

{

System.out.println( "Hello, world!" );

}

}

“main”method

create a java source file
Create(创建) a Java Source File
  • Step 1:
    • Start the Notepadeditor and type in the source code;
    • Save the source code in a directory the name of

HelloWorld.java

Java源程序后缀名

compile the source code
Compile(编译) the Source Code
  • Step 2: Compile the Source File into a .class File
run the program
Run(运行) the Program
  • Step 3: Run the program
java environment variables
Java Environment Variables(环境变量)
  • JAVA_HOME:
    • The path in which JDK is installed
    • provide general information to applications which need to use Java commands and JVM;
    • JAVA_HOME = C:\j2sdk1.4.2_08
java environment variables1
Java Environment Variables
  • Path:
    • used by Operating System to search the command to execute;
    • PATH =…;C:\j2sdk1.4.2_08\bin
java environment variables2
Java Environment Variables
  • CLASSPATH:

CLASSPATH = .; C:\j2sdk1.4.2_02\lib

  • ‘.’ — current path;
  • to tell JVM the path to find the class library.
java commands
Java Commands
  • javac - the Java compiler
  • java - the Java bytecode interpreter (JVM)
  • jdb - the Java debugger
  • javadoc – a documentation generator that lets you generate documentation from your Java source code and the Javadoc comments you place in your source code
  • jar- Java archive utility
java program structure
Java Program Structure
  • What is a Class(类)?
    • A class is a prototype that defines the variables and the methods common to all objects of a certain kind.
  • What is an Object(对象)?
    • Software objects are often used to model real-world objects in everyday life.
    • An object is a software bundle of related variables and methods.
  • An object is an instance(实例) of some class.
example 2 11
Example 2.1:

/***** HelloWorld.java *****/

//* Author: Mary

public classHelloWorld

{

public static void main( String[ ] args )

{

System.out.println( "Hello, world!" );

}

}

java program structure1
Java Program Structure
  • Comments(注释)
    • Anything between /* and */ or following // on a single line
    • Programmers use comments in their code to provide information to the reader on what the code is doing.
    • When a program is compiled, the compiler skipsall comments.
    • It is common (and good) practice to use a comment at the top of the code containing general information about the file (known as a header).
java program structure2
Java Program Structure
  • Class
    • All Java code must be part of a “class”.
    • Every class has a name:

public class HelloWorld

{……}

    • Braces { and } are used to mark the startand endof the class.
    • Other class information may also appear with the name:
      • A “public” class is one that can be referred to by other classes.

class name

modifier

components of classes
Components of Classes
  • Inside a class, there can be
    • fields(域): store values of some information
    • methods(方法): a collection of statements that performs a sequence of operations on the variables.
  • In our first program, we have zero attributes(域/属性)and one method.
example 2 2
Example 2.2

/***** Point.java *****/

//* Author: Mary

public classPoint {

public int x;

public int y;

public Point(int a; int b) { //constructor(构造函数)

x = a;

y = b;

}

public void print() { //method

System.out.print("The Point's coordinate is");

System.out.println("("+x+", "+y+")");

}

} // end of the class ‘Point’

method
Method(方法)
  • Each method has 2 parts:
    • a header
      • The header contains the name and other information about the method.
    • a body
      • The body describes what the method should do.
        • Braces { and } are used to mark the start and end of the method body.
        • A method body consists of a set of statements(语句).
example 2 12
Example 2.1:

/***** HelloWorld.java *****/

//* Author: Mary

public classHelloWorld

{

public static void main( String[ ] args )

{

System.out.println( "Hello, world!" );

}

}

method1
Method(方法)
  • In our first program Example 2.1, we have one method. The name of the method is main
    • main is a special name. It means:

“when you run the program, start here.”

  • The header ofmainmust be defined in the format as follows:
  • Our main method has only onestatement(语句).

public static void main(String[ ] args) {…}

statements
Statements(语句)
  • A statement (语句) represents an action or a sequence of actions.

System.out.println("Welcome to Java!");

    • a statement to display the greeting "Welcome to Java!" ;
    • Every statement in Java ends with a semicolon (;).
keywords
Keywords(关键字)
  • Reserved Words/keywords(保留字/关键字)
    • have a specific meaning to the compiler;
    • cannot be used for other purposes in the program.
    • eg.: class, public, static, and void
slide25
Java关键字
  • 具有特殊含义的字符序列,共48个。

Abstract default if private this

Boolean do implements protected throw

break double import public throws

byte else instanceof return transient

case extends int short try

catch final interface static void

char finally long strictfp volatile

class float native super while

const for new switch

continue goto package synchronized

example 2 21
Example 2.2

Class Header

/***** Point.java *****/

//* Author: Mary

public classPoint {

public int x;

public int y;

public Point(int a; int b) {

x = a;

y = b;

}

public void print(){

System.out.print("The Point's coordinate is");

System.out.println("("+x+", "+y+")");

}

} // end of the class ‘Point’

Attributes

Constructor

Method

assignment
Assignment(作业)
  • Download Eclipse & J2SDK(Java Software Development Tool), and install them on your computers.
  • To create, compile, and run the HelloWorld.java program on your own computer, and get familiar with the commands and process.