java Overview:
Java development can be summarized as follows several stages.
( 1 ) The first stage ( complete period ) : the JDK 1.0 (1995 launch ) a JDK 1.2 (1998 launch, the Java changed its name to the Java 2) ;
( 2 ) a second phase ( stationary phase ) : the JDK 1.3 a the JDK 1.4 ;
( 3 ) The third stage ( development stage ) : the JDK 1.5 (2005 launch ) a JDK 1.7 ( by Oracle after the acquisition launch ) .
General business will not use the latest stable version because poor performance.
And jdk1.7 = java7
In the development is divided into the Java SE, the Java EE, the Java ME , the following were interpreted this 3 difference directions.
( 1 ) J2SE : the Java 2 Platform Standard Edition (2005 changed its name years later as the Java SE) . It contains constitute Java Language core. Such as database access, interface definition, data structures, input / output, network programming.
(Java is the foundation of the entire two-stage are learning javaSE)
( 2 ) the J2EE : the Java 2 Platform Enterprise Edition (2005 changed its name years later as the Java EE) . Enterprise Edition ( Enterprise Edition ) includes J2SE all classes, and also contains classes for developing enterprise applications. For example, the EJB , Servlet , JSP , XML , transaction control, which is now Java main direction of application, like some banks or telecommunications systems are mostly based on this architecture. (Combination of page and systems)
( 3 ) J2ME : the Java 2 Platform Micro Edition (2005 changed its name years later as the Java ME) . Consumer electronics products for software development. Such as pagers, smart cards, mobile phone, PDA , set-top boxes.
(Development of mobile end, has been eliminated by an alternative Andrews)
About compiled and interpreted languages :
If the terms of a programming language, it should be divided into two types:
(1) compiled: learned C language students should know that there will be a compilation after the * .exe file for the user
use. ( First compiled at runtime )
(2) interpreted: as ASP language as directly to the code on the server interpreted.
All Java extension program files should be " * .java" , and any * .java program must first be compiled, will form after compiling a * .class files ( bytecode file ) , and then executed on the computer but the computer is not a computer program to explain the true sense of one, but a computer simulated by software and hardware - the Java virtual machine (the JVM the Java virtual machine.) .
In Java , all the programs are in Java running on the virtual machine. Java Virtual read and processed by the compiled platform-independent bytecode class files. Java interpreter is responsible for the Java code that virtual machines running on a particular platform.
Run java is a computer hardware and software simulated commonly known as java virtual machine (java virtual machine. Abbreviation jvm)
As long as any system installed java virtual machine (jvm) can be used as long as no relationship with the platform can be used in accordance with the jvm
About compiled and interpreted languages :
If the terms of a programming language, it should be divided into two types:
(1) compiled: learned C language students should know that there will be a compilation after the * .exe file for the user
use.
(2) interpreted: as ASP language as directly to the code on the server interpreted.
All Java extension program files should be " * .java" , and any * .java program must first be compiled, will form after compiling a * .class files ( bytecode file ) , and then executed on the computer but the computer is not a computer program to explain the true sense of one, but a computer simulated by software and hardware - the Java virtual machine (the JVM the Java virtual machine.) .
In Java , all the programs are in Java running on the virtual machine. Java Virtual read and processed by the compiled platform-independent bytecode class files. Java interpreter is responsible for the Java code that virtual machines running on a particular platform.
JDK installation, the Eclipse installation :
Installation steps refer to the documentation.
Java learning will never be able to crash, use EditPlus Notepad to edit the Java code that, until the time to learn the contents of the abstract classes, interfaces, such as re-use Eclipse this advanced development tools.
JRE (Java Runtime Environment Java Runtime Environment ) (can not run java compiler typically mounted on the customer's computer)
Including the Java Virtual Machine ( the JVM Java Virtual Machine ) and Java procedures required core class libraries, if you want to develop a good run Java programs, the computer only need to install the JRE can be.
JRE included JVM and core within the library
JDK (Java Development Kit Java Development Kit ) (to the developer installed)
JDK is available to Java developers, which contains the Java development tools, also includes the JRE . So install the JDK , you will not need to install separate JRE up.
JDK and JRE including the development program
java developer experience:
- The Java to write code to extension .java file.
- By javac to the command java compile files.
- By java to generate a command class were run file.
format:
cmd：
(1) public class definitions:
Class name and file name must be consistent, otherwise the program will not compile, in a * .Java in only one public class ;
(2) primary methods main () :
The main method indicates the start of a program, all the code are thus sequentially executed in Java main method should be placed in a class.
(3) the system output System.out.println () :
public static void main modifier positioning method is the method name (String [] as AGRS) is a list of parameters specified type String []