java基础：标识符和关键字
标识符解释：类名，变量名，以及方法名都被称为标识符标识符有哪些大约 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,priva
