JAVA中,标识符, 指用于给变量.类.方法名 等命名的名称.
1,标识以数字,字符,下划线,以及美元$符组成.(不能包括@、%、空格等),不能以数字开头. 2,不能与JAVA关键字重复
3,严格区分的大小写,(Flag和flag是两个变量) abstract assert boolean break byte case
catch char class const continue default do double else enum extends
final finally float for goto if implements import instanceof int
interface long native new package private protected public return
strictfp short static super switch synchronized this throw throws
transient try void volatile while 等