1. Keyword
Java is given a particular meaning of the word (all lowercase words)
const and goto as a reserved word, do not currently use.
2. Identifier
Is my i themselves to classes, interfaces, methods, variables from the name.
Composition rules:
May uppercase and lowercase letters, numbers, $, and _ (underscore) by the English composition.
note:
You can not start with a number, not as Java keywords, strict distinction between the English case, the identifier without spaces.
3.java naming convention
Common naming rules: See name EENOW
Package (that is, the folder for the class with the same name to distinguish): Words All lowercase domain name written backwards
Packet into a single stage and multi-stage packet (with intermediate. Separated )
Class or interface : it may be by one or more word-word
When a word: the first letter of the word capitalized
When more than one word: the first letter of each word capitalized
Method or variables : may be by one or more word-word
When a word: word in all lowercase letters
When more than one word: the beginning of each word from the second word capitalized
Constants : You can also by one word or more words
When a word: a word in CAPITAL LETTERS
When more than one word: words in CAPITAL LETTERS, in the middle of words separated by _
4. Comment
Text explanation for the program, annotated text will not be JVM (Java Virtual Machine) to explain the implementation.
Debugger can also help us to find errors in the code.
Divided into:
Single-line comments: // comment text
Multi-line comments: / * comment text * /
文档注释：/** 注释文字 */ （Java特有注释 可以用JDK提供的 javadoc 所解析，生成一个以网页形式体现的说明文档）
5.常量
在程序执行的过程中，其值不发生改变的量。
分类:
字面值常量
字符串常量：用双引号引起来的量
字符常量：用单引号引起来的量（只可以是一个字母或一个汉字）
整数常量：正整数 或 负整数
小数常量：带小数点的数
布尔常量：true 或 false
空常量： null
自定义常量（符号常量）
6.变量
在程序运行的过程中，其值会发生改变的量。