In-depth analysis of the first java program

When we learn java programming, the first Java program we start with is HelloWorld. Now let's go back and analyze the program in depth.

(Learning video sharing: java teaching video)

There are three steps to successfully run a Java program: write, compile, run

Write:

public class HelloWorld {
	
	public static void main(String[] args) {

		System.out.println("Hello, World!");

	}

}

Compile:

javac HelloWorld.java

Run:

java HelloWorld

Summary of the first Java program

1. Java program writing— Compilation-running process

编写：将编写的代码保存在一个以".java"结尾的源文件中；

编译：使用javac命令编译java源文件，这将会生成一个以".class"结尾的字节码文件，格式：javac 源文件名.java

运行：使用java命令解释运行由javac生成的以".class"结尾的字节码文件，格式：java 类名

2. Class declaration

You can declare multiple classes in a java source file, but at most one class can be declared public, and this is required The class name of a class declared as public must be the same as the source file name.

3. The entrance of the program

The entrance of the program is the main method, and the fixed format is:

public static void main(String[] args) {
	...
}

4. Output statement

System.out.print();	//只输出
System.out.println();	//先输出后换行

5. Execution statement The end of

Each line of execution statement ends with ";"

6. Comments

Categories: single-line comments, multi-line comments, document comments

Format:

Single-line comments: //
Multi-line comments: /* …*/
Documentation comments: /**…*/

Java API Documentation

Java API documentation is a description of how to use the class library provided by java. You can directly enter the API provided by Oracle's official website to view and use it.

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