List of Java keywords: Difference between revisions

Revision as of 14:14, 26 May 2009

Revision as of 05:35, 27 May 2009

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[[Image:Java keywords highlighted.png|thumb|A snippet of Java code with keywords highlighted in blue and bold font]]

In the [[Java (programming language)|Java programming language]], a '''keyword''' is one of 50 [[reserved word]]s which have a predefined meaning in the language; because of this, programmers cannot use keywords as names for [[variable#Computer (programming)|variables]], [[method (computer science)|methods]], [[class (computer science)|classes]], or as any other [[identifier]].<ref name="keywords">{{cite web |title=Java Language Keywords |url=http://java.sun.com/docs/books/tutorial/java/nutsandbolts/_keywords.html |work=The Java Tutorials |publisher=[[Sun Microsystems, Inc.]] |date=February 14, 2008 |accessdate=2008-12-02}}</ref> Due to their special functions in the language, most [[integrated development environment]]s for Java use [[syntax highlighting]] to display keywords in a different color for easy identification.{{Fact|date=December 2008}}

The following is a list of the keywords in Java, along with brief descriptions of their functions:<ref name="keywords" />

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:A type that defines the implementation of a particular kind of object. A class definition defines [[Object (computer science)|instance]] and class fields, [[Method (computer science)|methods]], and [[inner class]]es as well as specifying the [[Interface (computer science)|interfaces]] the class implements and the immediate [[Superclass (computer science)|superclass]] of the class. If the superclass is not explicitly specified, the superclass is implicitly {{Javadoc:SE|java/lang|Object}}.

;<code>[[Variable#Constant (programming)|const]]</code>

:Although reserved as a keyword in Java, <code>const</code> is not used and has no function.<ref name="keywords" />

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:The <code>for</code> keyword is used to create a [[for loop]], which specifies a variable initialization, a [[boolean expression]], and an incrementation. The variable initialization is performed first, and then the boolean expression is evaluated. If the expression evaluates to <code>true</code>, the block of statements associated with the loop are executed, and then the incrementation is performed. The boolean expression is then evaluated again; this continues until the expression evaluates to <code>false</code>.<ref name="for">{{cite web |title=The for Statement |url=http://java.sun.com/docs/books/tutorial/java/nutsandbolts/for.html |work=The Java Tutorials |publisher=Sun Microsystems, Inc. |date=February 14, 2008 |accessdate=2008-12-03}}</ref>

:As of [[Java version history#J2SE 5.0 (September 30, 2004) (EOL)|J2SE 5.0]],{{Fact|date=December 2008}} the <code>for</code> keyword can also be used to create a so-called "[[Foreach#Java|enhanced for loop]]", which specifies an [[Array data type|array]] or {{Javadoc:SE|java/lang|Iterable}} object; each iteration of the loop executes the associated block of statements using a different element in the array or <code>Iterable</code>.<ref name="for" />

;<code>[[GOTO|goto]]</code>

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:The <code>while</code> keyword is used to create a [[while loop]], which tests a [[boolean expression]] and executes the block of statements associated with the loop if the expression evaluates to <code>true</code>; this continues until the expression evaluates to <code>false</code>. This keyword can also be used to create a [[do-while loop]]; see ''<code>[[#do|do]]</code>''.<ref name="do-while" />

==[[Reserved word]]s for [[literal (computer science)|literal]] values==

;<code>[[Truth value|false]]</code>