Java's Hello world!

1 Introduction to Java language features

Unlike compiling this low-level computer programming language, Java, as a high-level programming language, requires a running environment, and the Java runtime is the JRE (Java runtime enviroment) just running Java programs. The JRE is enough. Java is the most important thing in the JRE Java Virtual machine, virtual machine is Java's soul ah Java to cross-platform, once compiled, everywhere, it is done by it. Now the language running on the JVM is not just Java Groovy,scala,ko Tlin and other visible JVMs are excellent, and the JVM's in-depth study is that we learned the basics of Java to get the EE version before we go back to the study.

The JDK (Java Development Kit) Development Kit is required for development.

2 JDK Download and installation

Official website: http://www.oracle.com/technetwork/java/javase/downloads/index.html download the corresponding system and the number of digits can be, one-click installation.

3 Configuration of environment variables

Computer Right-click Properties Advanced System Settings

Environment variables

The variable value of the new java_home in the system variable is the JDK installation directory

The new CLASSPATH value is. " JDK installation directory \lib. " The JAVA class library (content under the Lib folder) can be accessed under any path%java_home% is a reference to the JAVA_HOME system variable you just configured, and F:\Java is also available here.

Finally, the modification of an existing environment variable named path adds a value to the JDK installation path \ Bin

If it is Win7 or the previous Windows system, remember to separate the English semicolon from the previous variable name.

After the configuration, test it.

Win+r cmd into the command line

Type Javac

This interface is available.

4 Hello World Applet

Below hit a Java Hello World program file named Hello.java saved on the desktop

 Public class hello{    publicstaticvoid  main (string[] args) {        System.out.println ( "Hello World");}    }

View Code

　　

Video Version Link: https://www.bilibili.com/video/av12299042/

Java's Hello world!