1: Computer Overview (Learn)
(1) Computer (2) computer hardware (3) computer software system software: Window,linux,mac application software: Qq,yy, Fei Qiu (4) software development (understanding) Software: It consists of data and instructions. (Calculator) Development: The software is done. How to implement software development ? is to use development tools and computer language to make things come (5) Language Natural language: The computer language in which people communicate with each other: C,c + + of communication between man and computer , C#,java (6) man-machine Exchange graphical interface: Easy to operate DOS commands: Remember some common commands
2: Understanding and Shortcut keys of keyboard function keys
(1) function key recognition tab shift Ctrl ALT WinDOS space up or down enter prtSc (2 ) Shortcut keys Select all Ctrl+A copy Ctrl+C paste Ctrl+V cut Ctrl +X undo Ctrl+Z save Ctrl+s
3: Common DOS commands
Open the console windows+r run input cmd Enter, enter the console (1) common following drive symbol switch d: Enter the directory of the CD Javase CD Javase\day01\code the fallback CD for the catalog : CD Clear CLS exit exit (2) other several (understanding) Dir (directory): Lists files in the current directory and folder MD ( Make directory: Create directory rd (remove directory): Delete directory, different from delete file CD (change directory) changes the specified directory (enter the specified directory) CD.: Go back to the top level directory cd\: Rollback to root del (delete): Delete file, delete a bunch of suffix files *.txt exit: Exit DOS command line CLS: (Clear screen) Clear
4:java Language Overview
(1) History of the Java language Java's father JDK1. 4.2 JDK5 JDK7 (2) Java language features a number of small features, with a focus on two open source, cross-platform (3) The Java language is cross-platform, how can I assure you? (understanding) We explain it through the case of translation. for different operating systems, improve the different JVM to achieve. (4) The Java language Platform Javase javame--Android java EE
The role and relationship of 5:JDK,JRE,JVM
(1) function JVM: The development Environment of Jdk:java program to ensure the running environment of the Java language Cross-platform Jre:java program (2) Relationship Jdk:jre+ Tools JRE:JVM+ class Library
6:JDK download, install, uninstall
(1) download to official website.
for different operating systems, download different JDK versions to identify the operating system of the computer A: Can also go to Baidu search can.
B: I'll give it to you. (2) installation A: The green version of the decompression can be used B: The installation version must be step-by-step installation, generally as long as the click on the next note: It is recommended that all development-related software should not be installed in Chinese or a blank directory.
When prompted to install the JRE, you can choose not to install.
(3) Uninstall A: Green version directly delete folder B: Install version -- Add Remove program B: Through the Professional software Uninstall tool. (e.g. 360 software Manager uninstall)
The Installed path
Detect if the installation was successful
In the cmd input Java, you can know
7: The first program: HelloWorld case
class HelloWorld {public static void Span style= "COLOR: #000000" > main (string[] args) {System.out.println ( "HelloWorld" ); }} ( 1) program explains that the most basic unit of a A:java program is a class, so we define a class. Format: Class name example: Class HelloWorld B: When writing content in a class, enclose it in curly braces. To execute a c:java program, you must have the main method. Format: public static void main (string[] args) D : To point to those things, enclose them in curly braces. E: What are you going to do ? Today we just made a simple output format: System.out.println ( "HelloWorld" ); Note: The contents of "" 2
8: Common problems
(1) The extension is hidden, be sure to avoid how to find: Tools --Folder Options--View-- Remove the check mark of the hidden extension (2) I want the file name to match the class name. in fact, it is possible not to do so. However, note: Javac followed by the filename + extension Java followed by the class name without the extension (3) The Java language is strictly case-sensitive, please note. There is also the word don't write wrong. (4) See illegal characters: \65307 is definitely a Chinese problem. We write procedures that require punctuation marks to be all in English state. (5) The pairing problem of brackets. In general, the parentheses are paired up. (6) When the main method is not found in the class HelloWorld, define the main method as a certain format problem for the main method.
Operating principle
9:path Environment variables
(1) The role of the PATH environment variable guarantees that the Javac command can be run in any directory. Similarly, you can configure QQ, etc. (2) path configuration of two scenarios: A: Scenario 1 (understanding) B: Scenario 2 Find the location of the environment variable, in the system variable inside the NEW: variable name: java_home Variable Value: D : \develop\java\jdk1. 7. 0_60 Modify: variable name: Path Variable value:%java_home%\bin; previous content
The role of the PATH environment variable configuration
The execution of the program requires the use of external instruction Javac, but the javac instruction can only be in the bin directory under the JDK installation directory, so the program can only be written to the Bin directory program development process, the source code can not be written to the JDK installation directory, so you need to save the source program in any location of the specified directory ( English directory), so you need to make the JAVAC directive run in any directory
PATH environment variable configuration mode 1
By configuring the PATH environment variable, the directory in which the javac instruction resides, the bin directory under the JDK installation directory, is configured under the PATH variable to enable the javac instruction to run the WIN7,WIN8 system in any directory:
Right click on desktop computer → select Properties → select advanced system settings → select advanced tab → Click environment variables → system variables below find path→ double-click Path
Add the Bin directory under the JDK installation directory to the leftmost and add a semicolon
Test is configured successfully, run Javac in any directory of CMD
Helloworl.java can also be run on the D-Reel.
PATH environment variable configuration Mode 2-----recommended method
How to configure the PATH environment variable in reference form
Create a new variable name: Java_home to Java_home
Add Variable Value: JDK installation directory
Modify the JDK directory in the PATH environment variable%java_home%\bin;
Test can run successfully
PATH environment variable has precedence
CLASSPATH environment variable configuration mode----generally do not need to configure, a little understanding can
Role: Enables. class files in the Classpath directory to run in any directory
Create a new variable name: classpath
Value to the specified directory with the class file, using semicolons between multiple directories (;) split
Tip: You will typically add the configuration to the front of the directory. Configuration, even if the current directory, the. class file search for the current directory, and then based on the order of the directory configuration to find and run, so the configuration in the Classpath directory is in order
The difference between path and classpath
The PATH environment variable is a executable file, such as an. exe file, to the executable file in the current path to find, if not found to go to the path configured in the directory environment variable to find the CLASSPATH environment variables are recorded in the Java class running file is located
01-01java Overview doc commands, jdk\jre download installation, path, classpath configuration, common minor issues in development