1.1 Java Overview
As we all know Java is a programming language, programming language is used to write software. Then the use of Java in the end what can be used to write software? As you know a lot of software written in Java can be used, for example: QQ, Thunder, Taobao, Jingdong, etc., then what good Java compare it? That is our future in the Java development engineers work in the end what kind of software you want to write it?
the answer is:
- Internet: electricity providers, P2P, and so on;
- Enterprise applications: ERP, CRM, BOS, OA, and so on.
Internet software category they are more familiar, because we live can reach it. The enterprise applications are tailored for large enterprise software for work, so we may not understand. Now we just have to Java development engineers work to a general understanding.
On the basis of the class we'll learn the basics of Java, that JavaSE (Standard Edition) section. JavaSE not finished learning and the development of large-scale projects.
Employment class we will learn advanced knowledge of Java and the entire Java ecosystem, namely JavaEE (Enterprise Edition) section. After completing JavaEE section you can develop a variety of large-scale project.
1.2 Common DOS command
Preparation of source documents compiled after the operation needs to start, but in the Windows operating system to compile and run all need to understand the common DOS commands, so let's learn about common DOS commands (DOS commands knowledge of the Windows operating system is included).
DOS command is a command used in DOS console by pop-up DOS console is: win + R, then the output cmd, is not it looks a bit familiar, yes, that is JDK verify whether the installation was successful pops up a small black screen.
There are many DOS commands, we do not need to learn all the DOS command, we just need to learn to use Java in common DOS commands, as follows:
l clear screen: cls;
When n is too large content DOS console, clear screen command may be used, equivalent to "effaceurs";
n example: C: \> cls, and press Enter.
l :: handover letter;
n the case where we are in the C disk, if you want to go to other letter can use this command by default;
n example: C: \> E :, and then press the Enter key to E site.
l Enter the specified directory: cd;
n When we want to enter a directory can use this command;
n For example: D: \> cd develop, thus entering the D: \ develop directory, of course, you need to ensure that this directory exists;
n For example: D: \> cd develop \ Java, so we entered the D: \ develop \ Java directory.
l back one level: cd ..; 0
n When you need to return to the parent directory can use this command;
n For example: D: \ develop \ Java> cd .., and then press ENTER, returns to D: \ directory under develop.
Back letter l root: cd \;
n When the need to return to the current letter root can use this command;
n For example: D: \ develop \ Java> cd \, and then press ENTER, so that it returns to D: / a directory.
l Display information files and subdirectories in the current directory: dir;
N You can use this command when you need to view the current directory information of all files and subdirectories;
l run the application: full name of the program parameters
n when it is necessary to run an application you can use this command;
n For example when you want to run the Notepad program: D: \> C: \ windows \ notepad.exe, this will open the Notepad program, which you to C: \ same effect as double-clicking the program icon in the windows directory, because the Double-click to run the program support;
n may be omitted ".exe" suffix, for example: D: \> C: \ windows \ notepad, supra effect;
1.3 Java Development Environment Overview
Before you start to learn Java programming, we first need to install the Java development environment (JDK: Java Development Kit Java Development Kit).
You may ask: "Why should we install JDK it", in fact, everything needs to have his basic living environment, just like humans also need basic living environment (heaven, earth, water, air, ......). Development of Java programs is no exception, it also requires basic "living environment", that is, Java development environment (JDK).
As for the JDK contains something, now it is not the time to explain. Our task now is to immediately download it, install, and verify the installation was successful.
JDK version of our courses using JDK7, the current latest version is JDK8.
1.4 JDK download & install & check
JDK please download and install the required operating strictly in accordance with my other essay "JDK download Installation", if not in accordance with the requirements of the operation may cause unexpected problems. Not repeat them here!
Let's talk about how to verify the success of the JDK installation method. You do not need to know why he does it, only in strict accordance with the following steps:
- On keyboard press: WIN + R key, a window will pop up operation;
- In the Run window, enter: CMD, press the "OK" button, will pop up a DOS window;
- In the DOS window, enter: the JDK installation path \ bin \ java.exe.
There are pictures
If the result of the same picture, Congratulations, installation is successful; otherwise, the installation fails! ! ! Here are the most common installation fails sample:
- The system can not find the specified path: It may be because the JDK installation path input errors;
- Not an internal or external command, operable program or batch file: installation failed.
1.5 JDK and JRE
In the process of installing the JRE you may have noticed the term, let's talk about the relationship and the difference between the JRE and JDK.
l JDK: It is a Java development environment running on the computer programmers of course you want to install JDK;
l JRE: Java Runtime Environment Java runtime environment it is, if you do not develop only need to run Java programs, you can install the JRE. For example programmers to develop a program sold to end-users, users do not develop, you need only run the program, so the user can install the JRE on your computer.
l JDK contains JRE.
1.6 cross-platform features
l platform refers to the operating system (Windows, Linux, Mac).
l Java program can run on any operating system, write once, run everywhere
l need to rely on cross-platform Java Virtual Machine JVM (Java Virtual Machine)