The Java Tutorials have been written for JDK 8.Java教程是为JDK 8编写的。Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.本页中描述的示例和实践没有利用后续版本中引入的改进，并且可能使用不再可用的技术。See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.有关Java SE 9及其后续版本中更新的语言特性的摘要，请参阅Java语言更改。
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.有关所有JDK版本的新功能、增强功能以及已删除或不推荐的选项的信息，请参阅JDK发行说明。
The Jar tool provides a u option which you can use to update the contents of an existing JAR file by modifying its manifest or by adding files.
The basic command for adding files has this format:
jar uf jar-file input-file(s)
In this command:
Any files already in the archive having the same pathname as a file being added will be overwritten.
When creating a new JAR file, you can optionally use the -C option to indicate a change of directory. For more information, see the Creating a JAR File section.
Recall that TicTacToe.jar has these contents:
META-INF/MANIFEST.MF TicTacToe.class TicTacToe.class TicTacToe.java audio/ audio/beep.au audio/ding.au audio/return.au audio/yahoo1.au audio/yahoo2.au example1.html images/ images/cross.gif images/not.gif
Suppose that you want to add the file images/new.gif to the JAR file. You could accomplish that by issuing this command from the parent directory of the images directory:
jar uf TicTacToe.jar images/new.gif
The revised JAR file would have this table of contents:
META-INF/MANIFEST.MF TicTacToe.class TicTacToe.class TicTacToe.java audio/ audio/beep.au audio/ding.au audio/return.au audio/yahoo1.au audio/yahoo2.au example1.html images/ images/cross.gif images/not.gif images/new.gif
You can use the -C option to "change directories" during execution of the command. For example:
jar uf TicTacToe.jar -C images new.gif
This command would change to the images directory before adding new.gif to the JAR file. The images directory would not be included in the pathname of new.gif when it's added to the archive, resulting in a table of contents that looks like this:
META-INF/MANIFEST.MF META-INF/MANIFEST.MF TicTacToe.class TicTacToe.class TicTacToe.java audio/ audio/beep.au audio/ding.au audio/return.au audio/yahoo1.au audio/yahoo2.au example1.html images/ images/cross.gif images/not.gif new.gif