二.Java關鍵字

具有專門的意義和用途，不能當作一般的標識符使用，這些標識符稱爲保留字(reserved word),也稱爲關鍵字：

--系統關鍵字：

  abstract, assert,boolean, break, byte, case, catch, char, class,
  const, continue, default, do, double, else, enum,extends, final, finally, float, for, if,
        
  implements, import, instanceof, int, interface, long, native, new, 
  package, private, protected, public, return, short, static, strictfp, super, switch,
  synchronized, this, throw, throws, transient, try, void, volatile, while

  用於類的接口聲明：class extends implements interface
    包引入和包聲明：import package
    數據類型：boolean byte char short int long float double
    某些數據類型的可先值：false true null
    流程控制：break case continue default for do while if else return switch 
    異常處理：catch finally throw throws try
    修飾符：abstract final native private protected public static synchronized transient volatile
    操作符：instanceof
    創建對象：new
    引用：this super
    方法返回類型：void