Java4android (Basic concept)

1. Configuration of environment Variables : Path key value: Location of bin folder

Classpath key value:.

2. First HelloWorld:

public class hello{public static void Main (String args[]) {System.out.print ("Hello world!");}}

3. What are environment variables?

Environment variables are usually used in the operating system to specify some parameters that the operating system needs to run, typically a series of key-value pairs

For example, some classic variable values, windir: is the installation location of Windows; OS: The version of the operating system; The core number of NUMBER_OF_PROCESSORS:CPU.

where the PATH environment variable works:

The path environment variable is the operating system external Command search path (the path value is a series of paths that are searched and executed at the command line when the file is executed)

The CLASSPATH environment variable is the class file search path where the value is (. ) represents the current directory

What's in 4.JDK?

Commands in Bin:java such as, Javac Java.exe

Examples in the Demo:sample:java

Content of the Include:c language

Jre:java Run-time environment

Package files required by the Lib:java

Src.zip:java part of the JDK source file

5. What is a JRE?

The JRE is the Java Runtime Environment, the Java Run environment, which includes the following sections:

Java Virtual Machine (JVM) Java Vsan, a computer that is virtual by software

Java platform core class file;

Other support files.

SOURCE file---Compiler---->class file---virtual machine----> Individual operating system executables