Crazy God said java study notes --- JAVA development environment to build

JAVASE

JAVA development environment construction

• JDK download and installation
• Configure environment variables
• JDK catalog introduction
• HelloWorld and simple grammar rules
• Notepad++ installation and use

JAVA download and installation

Uninstall JDK

1. Delete the Java installation directory

2. Delete JAVA_HUME

3. Delete the directory about Java under the environment variable path

4.Java - version

Install JDK

1. Baidu search JDK8, find the download address

2. Agree to the agreement

3. Download the version corresponding to the computer

4. Double-click to install JDK

5. Remember to install to the path

6. Configure environment variables

​ 1. My Computer -> Advanced System Settings -> Environment Variables

​ 2.Environmental variables-->JAVA_HOME

​ 3. Configure path variables, java\jdk\bin and java\jdk\jre

7. Test whether the JDK is installed successfully

​ 1. Open cmd

​ 2.java -version

java file

bin directory

Put some executable files, such as java, javac (compiler)

include directory

Put some C voice header files

jre directory

Operating environment

lib directory

Some library files of java

src.zip

Resource files, various java classes and basic source code

HelloWorld

1. Create a folder at will, store the code

2. Create a new java file

   • The file extension is .java
   • Hello.java
   • [Note] The system may not display the file extension, we need to open it manually

3. Write code

   public class Hello//public class 类+名字
   {
         
         
   	public static void main(String[] args){
         
         //修饰符关键字，main方法，String[] 参数。
   	System.out.print("Hello,World!");
   		}
   }
   

4. Compile javac java file, will produce a class file

5. Run class file, java class file
   

   Possible problems

   1. The size of each word cannot be a problem, Java is case sensitive
   2. Try to use English;
   3. The file name and class name must be consistent, and the first letter must be capitalized
   4. Chinese symbols are used