Extract nested Jar File

Okay, I've been looking all day for solutions to this problem and nothing I've found pinpointed the solution, so if anyone would rather point me to another site, that's great.
I have a .jar installer ( installer.jar ) that contains the installer code and a nested jar file ( program.jar ).
In my experience, plain text files work great in the "getInputStream() -> FileWriter.write()" method, but my way of handling images requires javax.imageio.ImageIO, and i'm hoping something similar exists for jars.
ALL+* i want to do is extract that jar file into the current directory, but the ZipEntry.getInputStream() method didn't work, and JarInputStream just confuses me.
If anyone has links to other topics or source code to point to how a jarfile can be extracted.

Thanks for the help.
After looking around and finally noticing the Pack200 package, I have the answer!
JarFile jf = new JarFile( "outside.jar" );
JarOutputStream jos = new JarOutputStream( new FileOutputStream( new File( "inside.jar" ) ) );
Pack200.newUnpacker().unpack( jar.getInputStream( jar.getEntry( "inside.jar" ) ), jos );
jos.close();This creates a JarOutputStream that will write to the FileOutputStream forever until closed.
The Pack200 Unpacker takes the inputstream and outputs it to the JarOutputStream.
When the unpack method returns, the jar file is ready. Close the jar output stream and you have a workable jar!

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>
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