Javase01-Getting Started

1. Getting Started with Java

　　Java: A high-level object-oriented programming language introduced by Sun (Stanford University Network, Stanford University Inc.) in 1995.

　　SUN:2009 was acquired by Oracle (Oracle Corporation).

　　James Goslin: The father of Java.

　　Java History:2004 j2se1.5 release, is a milestone in Java development. and renamed to Java SE 5.0;

2005 Sun Company Public Java SE 6.0,java various versions are renamed;

J2ee→java EE;

J2se→java SE;

J2me→java ME;

Acquired by Oracle (Oracle Corporation) in 2009.

　Java three major technical architecture: Javase/javaee/javame (renamed after Java5.0 version)

　　Java Features: simple, object-oriented, distributed, compiled and interpreted, robust, secure, portable cross-platform, high performance, multi-threading, dynamic

Portability (cross-platform): Runs through a Java virtual machine on each platform. Java virtual machines are not cross-platform

　　Development environment for Java:

JDK (Java Development Kit) Java Development Kit

　　　　JRE (Java Runtime Environment) Java Runtime Environment

JVM (Java vsan Machina) Java Virtual machine

　　　　JDK = JRE + compile tools;

　　　　JRE = JVM + The class library provided by Sun Company;

　　 Development environment Construction:

　　　　* Download JDK and install

* Configure environment variables (increase JAVA_HOME=JDK installation directory, add classpath=., modify Path=%java_home%\bin)

　　The first program-helloworld:

　　　　1) write the source file with Notepad, the file name is "Helloworld.java";

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

2) Compile: Execute javac helloworld.java→helloworld.class in cmd window

3) Execute: Java helloworld→ get result output Hello world!

Common cmd commands

–MD: Create directory –dir: Lists files in the current directory and folders –rd: Delete directory –CD: Enter the specified directory –CD. : Back to previous level directory –cd/: Rollback to root –del: Delete file –exit: Eject dos command line – root drive: Toggle root Letter E:Java operating mechanism . java files are generated through Javac.exe compilation. class files run with Java.exe (JVM load) to get results 　　　　

Java is both a compiled language and an interpreted language

Java program composition: Java source files (. java) and bytecode files (. Class)

　　Be aware that:

　　　　Java language is strictly case sensitive

　　　　A Java original file can have more than one class, but there can be only one class defined as public decoration;

　　　　If the public class is included in the source file, the source file must have the same name as the public class;

When a source file contains n Java classes, an n-bit bytecode file is generated after compilation, that is, each class generates a separate class file, andThe byte-code file name is the same as its corresponding class name；

　　　　

　　

　　　　

Javase01-Getting Started