20145122 the first week of Java Program Design Study summary

This week's Java learning has begun.

First I understand the difference and connection between JVM, JRE and JDK. JDK: (Java Development Kit). The JDK is the core of the entire Java, including the Java Runtime Environment JRE, Java Tools, and the Java base Class library. jdk=jre+jvm+ other. Running Java programs generally requires the user's computer to install the JRE environment, no Jre,java programs can not run, and without Java programs, the JRE is useless. JRE: (Java Runtime Environment), not a development environment, so it does not contain any development tools. JVM: (JAVA virtual machine). The JVM is part of the JRE , a fictional computer that is implemented by simulating various computer functions on a real computer.

I then downloaded the JDK from the official website and installed it, and then started the configuration of the environment variables. First right click on Computer > Properties > Advanced system Settings > Advanced > Environment variables to find path and classpath for editing.

After configuring the environment variables, I learned some common DOS commands.

• Dir: Lists the files and folders in the current directory
• MD: Creating a Directory
• RD: Deleting a directory
• CD: Enter the specified directory
• Del: Delete Files
• Copy: Copying files
• xcopy: Copy Directory
• Tree: List directory tree
• ren: file name change
• Type: Display file contents
• CLS: Clear Screen
• Exit: Exit DOS command line

With this knowledge in hand, I use Java development tools to learn to knock a simple code on a book.                          ,         &NB Sp                          ,         &NB Sp                          ,         &NB Sp    

The Javac command is used to compile the Java source file into a class bytecode file, and after running the javac command a file of Aaa.class is available, and the Java command can run the class bytecode file, which is the file directory and the program running results.

• Self-made code run successfully, the mood is very excited. But there are a few things in the process that we need to be aware of in the first place.
  • The extension is. java. That's why you have to have the Explorer display the extension name.
  • The main document name and class name must be the same, and the class name refers to the name after the class keyword.
  • Also note the case of each letter. The Java program distinguishes the case of letters. System and system are different names for Java programs.
  • A space can only be half-width spaces or tab characters.

Learning Experience: in Java Learning, you have to practice more.    In the study of practice, in the practice of learning, learn lessons learned, so as to achieve greater progress.

20145122 the first week of Java Program Design Study summary