java中的null到底是保留字还是关键字？

xiaolu_dl 2011-07-13 09:22:15

java中的null到底是保留字还是关键字？，说什么的都有，希望能给个准确答案！谢谢！

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Spring源码解析 2011-07-13

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学习！！！！

飞跃颠峰 2011-07-13

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[Quote=引用 12 楼 xiaolu_dl 的回复:]

null和NULL有什么区别,会不会大写的不是，小写的才是，我刚刚试了，小写的回变色，大写的不会
[/Quote]

Java是大小写敏感的，大写的NULL没有任何含义，你可以把它当变量名或函数名用。小写的null代表一个空对象。

xiaolu_dl 2011-07-13

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null和NULL有什么区别,会不会大写的不是，小写的才是，我刚刚试了，小写的回变色，大写的不会

xiaolu_dl 2011-07-13

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答案是 B，只有NULL不是，

龙四 2011-07-13

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《Java语言规范》第三版第三章写的很明确：

3.9. Keywords
The following character sequences, formed from ASCII letters, are reserved for use as keywords and cannot be used as identifiers (§3.8):

Keyword: one of

abstract continue for new switch

assert default if package synchronized

boolean do goto private this

break double implements protected throw

byte else import public throws

case enum instanceof return transient

catch extends int short try

char final interface static void

class finally long strictfp volatile

const float native super while

The keywords const and goto are reserved, even though they are not currently used. This may allow a Java compiler to produce better error messages if these C++ keywords incorrectly appear in programs.

While true and false might appear to be keywords, they are technically Boolean literals (§3.10.3). Similarly, while null might appear to be a keyword, it is technically the null literal (§3.10.7).

所以，null，true，false不是关键字，但goto，const却是关键字

huntor 2011-07-13

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[Quote=引用 2 楼 xiaolu_dl 的回复:]

10、如下哪些不是java的关键字？
A）const B）NULL C） false D）this E) native

那这道题你觉得该选什么？
[/Quote]
B C

huntor 2011-07-13

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http://download.oracle.com/javase/tutorial/java/nutsandbolts/_keywords.html
[Quote]Java Language Keywords
Here is a list of keywords in the Java programming language. You cannot use any of the following as identifiers in your programs. The keywords const and goto are reserved, even though they are not currently used. true, false, and null might seem like keywords, but they are actually literals; you cannot use them as identifiers in your programs.

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

* not used
** added in 1.2
*** added in 1.4
**** added in 5.0 [/Quote]

qybao 2011-07-13

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java keywords

[keywords list]
　　abstract boolean break byte case
　　catch char class continue default
　　do double else extends false
　　final finally float for if
　　implements import instanceof int interface
　　long native new null package
　　private protected public return short
　　static super switch synchronized this
　　throw throws transient true try
　　void volatile while
　　
[reserved words]
　　const，goto