Editing JavaLanguage (section)

==Packages and Imports==
Java allows you to group classes in a collection called package. Just as you have nested subdirectories on your disk, you can organize packages using levels of nesting.
To add a file to a package insert the line

 '''package''' <PackageName>;

to your file. It must be the first line after any comment. Java code that is part of a package has access to all classes (public and non-public) in the package and to all non-private methods and fields in all those classes.
Everything in the java.lang package is automatically imported into every Java program. There you do not need to specify a package prefix in front of e.g. the system object. The java.lang packages contains the following parts:
Math
...
You can import special classes of a package or all classes of a package (s. example (x)), e.g.:

 '''import''' ['''static'''] <Part1>.<PartN>.('''*'''|<ClassName>)''';'''

 import java.applet.Applet;
 import java.awt.*;            // * is only allowed for a single package

Importing all classes in a package is simpler. It has no negative effect on compile time or code size, so there is generally no reason not to do it. Wenn es zwei packages gibt, die eine Klasse mit dem gleichen Namen enthalten, können nicht beide importiert werden, sondern eine muss über den voll qualifizierten Namen verwendet werden. Wenn die Klasse die importiert wurde nicht als *.class file vorliegt, wird sie implizit durch das import statement übersetzt. Kann sie z.B. wegen Syntaxfehlern nicht übersetzt werden, wird auch die importierende Datei nicht übersetzt.
All files of a package must be located in a subdirectory that matches the full package name. These subdirectories need not branch off from the root directory; they can branch from any directory in the CLASSPATH environment variable. JVM looks for <CLASSPATH>\<PACKAGENAME_PART1>\..\<PACKAGENAME_PARTN>\<CLASSNAME>.CLASS. The files can also be located in a CLASSES.ZIP file with the correct path information.
If no package statement is specified the class is thrown into a default package with all other package-less classes and all the non-private members are visible there. In 1.4 you can no longer import a class from the default package. You can only import a class that is in a named package. If your classes are in the default package, you do not need to use the import statement. Otherwise, you will need to package the classes or only use the default package.