1. Java Import Statement Copyright © 1997-2010 Curt Hill
This is the media computation version
Copyright © Curt Hill

2. Import Statement Gives access to existing classes and interfaces
Similar to #include of C
Usually first lines in file
Follows package, if present
Often follows comments
Example: import java.awt.Color;
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3. Import Form import is a keyword
Following that is the class you want to have access to
Wildcards can be used: import java.awt.*;
Using wildcards may slow the compile by 10% and who cares?
Object code will usually be same
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4. Directories Java grew up in a UNIX environment
Its import statement reflects this tree shaped directory
Each dot represents a boundary between one directory and another
Thus the import import java.awt.Color; is in directory: java/awt and the file is named Color.CLASS
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5. Tree Shaped Directories
The disk of most file systems contains two types of files:
Directories
Files
Each directory may then also contain other files and other directories
First seen in MULTICS but popularized by UNIX
Appeared in DOS 2 and later
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6. JAR Files Java also has its own archive file: JAR
JAR stands for Java ARchive
A JAR file has exactly the same format as a zip file
It may be maintained by zip utilities that allow different extensions
A JAR or ZIP file may also contain a directory structure
An import may reference the directory structure within a JAR file
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7. Common imports Basics in Java.Lang need no import
Applets will usually use: import java.applet.*; import java.awt.*;
Applications may also use: import java.io; import java.net; import java.util;
Developed code may also be imported
Copyright © Curt Hill

8. Example The following picture shows a Windows C: disk
It contains several directories and files
The Java runtime is in the Program Files directory
The runtime contains a JREn.jar
This contains where imports may be found, especially these:
import java.awt.Color;
import java.utils.Scanner;
import java.awt.*;
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9. Tree Shaped Directories
C: Disk
dir1 …
Programs …
Windows …
File1
JRE
File1
java
awt
utils
Color.class …
JButton.class …
Scanner.class
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10. Developed Code World and Turtle are classes not part of the JRE
If incorporated into a JAR file they may be accessed with an import
Otherwise the IDE may be directed to make them part of the global scope
Copyright © Curt Hill