Java package: Difference between revisions

Revision as of 15:02, 3 May 2020

Revision as of 18:00, 11 May 2020

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In a Java source file, the package that this file's class or classes belong to is specified with the <code>package</code> [[keyword (computer programming)|keyword]]. This keyword is usually the first keyword in the source file. At most one package declaration can appear in a source file.

<sourcesyntaxhighlight lang="java">

package java.awt.event;

</syntaxhighlight>

</source>

To use a package's classes inside a Java source file, it is convenient to import the classes from the package with an <code>import</code> declaration. The following declaration

<sourcesyntaxhighlight lang="java">

import java.awt.event.*;

</syntaxhighlight>

</source>

imports all classes from the <code>java.awt.event</code> package, while the next declaration

<sourcesyntaxhighlight lang="java">

import java.awt.event.ActionEvent;

</syntaxhighlight>

</source>

imports only the <code>ActionEvent</code> class from the package. After either of these import declarations, the <code>ActionEvent</code> class can be referenced using its simple class name:

<sourcesyntaxhighlight lang="java">

ActionEvent myEvent = new ActionEvent();

</syntaxhighlight>

</source>

Classes can also be used directly without an import declaration by using the fully qualified name of the class. For example,

<sourcesyntaxhighlight lang="java">

java.awt.event.ActionEvent myEvent = new java.awt.event.ActionEvent();

</syntaxhighlight>

</source>

does not require a preceding import declaration.