JAVA基础语法

JAVA基础语法

注释

• 单行注释
• 多行注释
• 文档注释

public class HelloWorld {
    public static void main(String[] args) {
        //单行注释
        //输出一个hello world
        System.out.println("hello world!");
        /*
        我是多行注释
        我是多行注释
        我是多行注释
         */

        //javaDoc:文档注释   /**    */
        /**
         * @Author 作者
         * @description
         */

        //有趣的代码注释

        /*
         *   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
         *   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!`   `4!!!!!!!!!!~4!!!!!!!!!!!!!!!!!
         *   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!   <~:   ~!!!~   ..  4!!!!!!!!!!!!!!!
         *   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  ~~~~~~~  '  ud$$$$$  !!!!!!!!!!!!!!!
         *   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  ~~~~~~~~~: ?$$$$$$$$$  !!!!!!!!!!!!!!
         *   !!!!!!!!!!!`     ``~!!!!!!!!!!!!!!  ~~~~~          "*$$$$$k `!!!!!!!!!!!!!
         *   !!!!!!!!!!  $$$$$bu.  '~!~`     .  '~~~~      :~~~~          `4!!!!!!!!!!!
         *   !!!!!!!!!  $$$$$$$$$$$c  .zW$$$$$E ~~~~      ~~~~~~~~  ~~~~~:  '!!!!!!!!!!
         *   !!!!!!!!! d$$$$$$$$$$$$$$$$$$$$$$E ~~~~~    '~~~~~~~~    ~~~~~  !!!!!!!!!!
         *   !!!!!!!!> 9$$$$$$$$$$$$$$$$$$$$$$$ '~~~~~~~ '~~~~~~~~     ~~~~  !!!!!!!!!!
         *   !!!!!!!!> $$$$$$$$$$$$$$$$$$$$$$$$b   ~~~    '~~~~~~~     '~~~ '!!!!!!!!!!
         *   !!!!!!!!> $$$$$$$$$$$$$$$$$$$$$$$$$$$cuuue$$N.   ~        ~~~  !!!!!!!!!!!
         *   !!!!!!!!! **$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$Ne  ~~~~~~~~  `!!!!!!!!!!!
         *   !!!!!!!!!  J$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$N  ~~~~~  zL '!!!!!!!!!!
         *   !!!!!!!!  d$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$c     z$$$c `!!!!!!!!!
         *   !!!!!!!> <$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$> 4!!!!!!!!
         *   !!!!!!!  $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$  !!!!!!!!
         *   !!!!!!! <$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$*"   ....:!!
         *   !!!!!!~ 9$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$e@$N '!!!!!!!
         *   !!!!!!  9$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$  !!!!!!!
         *   !!!!!!  $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$""$$$$$$$$$$$~ ~~4!!!!
         *   !!!!!!  9$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$    $$$$$$$Lue  :::!!!!
         *   !!!!!!> 9$$$$$$$$$$$$" '$$$$$$$$$$$$$$$$$$$$$$$$$$$    $$$$$$$$$$  !!!!!!!
         *   !!!!!!! '$$*$$$$$$$$E   '$$$$$$$$$$$$$$$$$$$$$$$$$$$u.@$$$$$$$$$E '!!!!!!!
         *   !!!!~`   .eeW$$$$$$$$   :$$$$$$$$$$$$$***$$$$$$$$$$$$$$$$$$$$u.    `~!!!!!
         *   !!> .:!h '$$$$$$$$$$$$ed$$$$$$$$$$$$Fz$$b $$$$$$$$$$$$$$$$$$$$$F '!h.  !!!
         *   !!!!!!!!L '$**$$$$$$$$$$$$$$$$$$$$$$ *$$$ $$$$$$$$$$$$$$$$$$$$F  !!!!!!!!!
         *   !!!!!!!!!   d$$$$$$$$$$$$$$$$$$$$$$$$buud$$$$$$$$$$$$$$$$$$$$"  !!!!!!!!!!
         *   !!!!!!! .<!  #$$*"$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$*  :!!!!!!!!!!!
         *   !!!!!!!!!!!!:   d$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$#  :!!!!!!!!!!!!!
         *   !!!!!!!!!!!~  :  '#$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$*"    !!!!!!!!!!!!!!!
         *   !!!!!!!!!!  !!!!!:   ^"**$$$$$$$$$$$$$$$$$$$$**#"     .:<!!!!!!!!!!!!!!!!!
         *   !!!!!!!!!!!!!!!!!!!!!:...                      .::!!!!!!!!!!!!!!!!!!!!!!!!
         *   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
         *
         */

    }
}

---

标识符

• 关键字
• Java所有的组成部分都需要名字。类目、变量名以及方法名都被称为标识符。

标识符注意点

• 所有标识符应该以字母（A-Z或者a-z）、美元符($)、下划线(_)开始
• 首字符之后可以是字母（A-Z或者a-z）、美元符($)、下划线(_)或者数字的任何字符组合
• 不能使用关键字作为变量名或者方法名
• 标识符大小写敏感
• 合法标识符举例：age、$salary、_value、__1_value
• 非法标识符举例：123abc、-salary、#abc
• 可以使用中文名但是不建议，也不建议使用拼音