Java Learning (i): Java Introduction and its platform, development environment configuration and construction

Java Introduction and configuration and construction of platform and development environment
1. Introduction to Java
Java is an object-oriented programming language with many features such as cross-platform, portable, distributed, simple, extensible, and so on. Java can be used for desktop applications, Web applications, distributed systems and applications such as embedded development.

Java contains 3 different versions, J2ME/J2EE/J2SE (mini/Enterprise/Standard).

2, the JDK download and installation, configuration

(1), jdk:http://www.oracle.com/technetwork/java/javase/downloads/index.html

(2), configure the JDK: you need to configure two environment variables: path and classpath (case insensitive). As shown in the following:

Input: path and C:\Program files\java\jdk1.8.0_45\bin;

Input:CLASSPATH and C:\Program Files\java\jdk1.8.0_45\lib\dt.jar; C:\Program Files\java\jdk1.8.0_45\lib\tools.jar;

Finally, verify that the JDK is configured successfully by entering CMD in a DOS environment, then entering Java-version, enter, and output as the content proves the configuration was successful.

3. Download and installation of Eclipse

Eclipse: http://www.eclipse.org/downloads/(directly unzip, run the application. ）

Or

MyEclipse: http://downloads.myeclipseide.com/(myeclipse not free)

4. Java operating mechanism

Java programs must be written, compiled, and run in three steps. This is the Java source file (*.java)->java Compiler---bytecode file (*.class)->java interpreter.

5. Creation of the first Java program (two methods)

5.1. Direct method

(1), create a new *.java file (you can use Notepad to edit, change the suffix name), enter the code;

public class HelloWorld {public static void main (string[] args) {System.out.println ("Hello world!");}

(2), compile Javac Xxxx.java, run Java XXXX, correctly compile and output instructions to execute the program successfully, such as.

5.2. Eclipse Law

(1), File->new->java Project, enter MyProject, click Finish.

(2), under the MyProject project, right click on src to select New->file, create a new *.java file.

(3), input code, compile and run.

public class Welcome {public static void main (string[] args) {System.out.println ("Welcome to Java world!");}}

(4), the correct output results, as shown.

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Java Learning (i): Java Introduction and its platform, development environment configuration and construction