1. Common DOS Commands (master)D: Enter the drive letter switch dir (directory): List files in the current directory and folder MD (make directory): Create directory Rd (remove directory): Delete directory CD (change D irectory) Change the specified directory (enter the specified directory) CD. : Back to previous level directory cd\: Rollback to root del (delete): Delete files, delete a bunch of suffix-like files *.txt exit: Exit DOS command line CLS: Clear screen
2. Java language Platform versionJ2SE (Java 2 Platform standard Edition) is a solution for developing common desktop and business applications. The technology system is the basis of the other two, can be completed some desktop application development j2me (Java 2 Platform MICR O Edition Small Edition is a solution for the development of electronic consumer products and embedded Devices Java 2 Platform Enterprise Edition is a solution for developing applications in enterprise environments the technologies included in this technology Servlet, JSP, etc., mainly for Web application development
3. Java language featuresSimple interpretative object-oriented high performance distributed processing multithreading robustness dynamic structure neutrality security
Open Source S
Cross-platform
4. What is cross-platform? Applications written in the Java language can be run on different system platforms. What is the principle? Just install a Java Virtual machine (JVM Java VM) on the operating system that needs to run the Java application. The JVM is responsible for the operation of the Java program in the system.
JRE (Java Runtime Environment Java Run environment) |
including Java virtual machines (JVM Java) and the core class libraries required by Java programs, if you want to run a well-developed Java program, you only need to install the JRE on your computer. |
JDK (Java Development Kit Java Development Kit) |
The JDK is available to Java developers, which includes Java development tools and the JRE. So with the JDK installed, you don't have to install the JRE separately.
Development tools: Compilation Tools (Javac.exe) packaging Tools (Jar.exe), etc. |
In simple terms: Java programs developed using the JDK are delivered to the JRE to run. (1) function JVM: Securing the Java language across platforms Jre:java the operating environment of the program Development environment of Jdk:java program (2) Relationship jdk:jre+ Tools jre:jvm+ Class Library |
5. The difference between path and classpathThe 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
(1) CLASSPATH environment variable configuration methodCreate a new variable name: The Classpath value is set to the specified directory with the class file, and semicolons are used between multiple directories (;) Partitioning: Enables. class files in the Classpath directory to run tricks in any directory: typically add the configuration to the front of the directory. Configuration, even if the current directory, so that the. class file search first search the current directory, and then according to the order of the directory configuration to find, and then run, so the Classpath directory The configuration is in sequence
(2) Path environment variable (master)(1) The role of the PATH environment variable guarantees that the Javac command can be run in any directory. The same can be configured QQ and other (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
(3) CLASSPATH Environment variables (understanding)(1) The function of the CLASSPATH environment variable ensure that the class file can be run in any directory (2) CLASSPATH environment variable configuration find the location of the environment variable, new in the system variable: variable name: Classpath Variable Value: E:\JavaSE\day01\code\HelloWorld case
Java Basic Course Learning notes (1)
