What are java annotations?

Comments are an important component of a language, such as C language, HTML language, and PHP language. They all have their own comment tags. Of course, as an important language, Java is certainly no exception. A program with comments is a real program, so that others and yourself can understand it, read it faster, and greatly improve work efficiency. Now let’s talk about Java annotations.

java annotations

In the process of writing Java, we need to annotate some programs, except It is convenient for ourselves to read and for others to better understand our program, so we need to make some comments, which can be programming ideas or the functions of the program. In short, it is to facilitate ourselves and others to better read.

Classification and function of Java comments

Java comments are roughly divided into two categories:

1. Single-line comments:

After the code line, use "//" to separate the code, and enter the explanation of the entered code after the double slashes. For example:

public class HelloWorld{		//关键字 class 声明类的定义，还帮助编译器理解它是一个类的声明，其后边的{}标志着程序的开始和结束

	public static void main(String [] args){	//关键字 public 是一个访问说明符，控制类成员的可见度和作用域，关键字 static 允许直接调用 main( ) 方法，而无需创建类的对象。
		System.out.println("HelloWorld");	//输出“HelloWorld”。
	}
}

2. Multi-line comments

A single-line comment can only be written in one line, and it cannot be changed with the Enter key, but we have multiple lines in Java Comment tag

/* ...... */ 
/**……*/

The first type of multi-line comment, the content of the comment will not appear in the document generated by javadoc. Single-line comments are similar to it.

The second type of multi-line comment, the content of the comment will be written into the document generated by javadoc. The source code is:

/**
*I am happy
*20202020
*这是一个多行代码，这个多行注释，可以显示help/index.html上面
*/
/*
* I am very happy
*202020
*这是第二类多行注释，不可以显示在help/index.html上面
*/
public class HelloWorld{ //关键字 class 声明类的定义，还帮助编译器理解它是一个类的声明，其后边的{}标志着程序的开始和结束

	public static void main(String [] args){ //关键字 public 是一个访问说明符，控制类成员的可见度和作用域，关键字 static 允许直接调用 main( ) 方法，而无需创建类的对象。
		System.out.println("HelloWorld"); //输出“HelloWorld”。
	}
}

Type in the cmd window where the file is located:

and the above cmd content will appear content, so what is this? At this time, a help file will appear on our C drive. Click on it. There is an index.html web page. Click on it:

You can see that the second type is multi-line. The comment is where the black arrow points, and the first type and single-line comments are not visible.

This is the content of java comments. Java comments play a great role in the use of Java. You must use comments frequently.

Recommended learning: Java video tutorial

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