Jar

Jar

Translation: Cherami

Email: cherami@163.net

Original: http://developer.java.sun.com/developer/techtips/2000/tt0411.html

Have you tried to use the JAR file archive? You may have heard a UNIX tool called "TAR" or tape archive file, which is usually used to back up a set of files. In JDK 1.1 and later, there is a similar tool "jar" or a Java packer. The following is a method of use.

Create a JAR package using the following:

$ jar cf archive.jar file1 file2 ...

After creating the archive package, you can list the contents:

$ jar tf archive.jar

And you can extract the files from it:

$ jar xf archive.jar [file1 file2 ...]

Why is the JAR tools are important? After all, there are many different zip tools for packaging and compress files. Its important use is to bind multiple class files. A set of class files can form a package or library. For example, in Windows 95 or NT, you can say:

ClassPath = "lib1.jar; lib2.jar;"

Another very important usage of it is to optimize the loading of the applet. Consider the simple applet below:

// applet.java

Import java.awt. *;

Import java.applet. *;

Public class applet extends applet {

Public void Paint (Graphics G)

{

String s = message.getInetIntro ("INTRO");

g.drawstring (s, 25, 25);

}

}

It visits a secondary class:

// Message.java

Public class message {

Public Static String GetIntro (String T)

{

IF (t! = null)

Return T;

Else

Return "Hello World!";

}

}

You call this applet with HTML code, for example: