从jar中取出指定的文件

import java.io.*;
import java.util.jar.*;
import java.util.zip.*;

public class ExtractFromJAR {

public void extractMyDBFromJAR(String dest){
try {
String home = getClass().getProtectionDomain().
getCodeSource().getLocation().toString().
substring(6);
JarFile jar = new JarFile(home);
ZipEntry entry = jar.getEntry("mydb.mdb");
File efile = new File(dest, entry.getName());

InputStream in = new BufferedInputStream(jar.getInputStream(entry));
OutputStream out = new BufferedOutputStream(new FileOutputStream(efile));
byte[] buffer = new byte[2048];
for (;;)  {
int nBytes = in.read(buffer);
if (nBytes <= 0) break;
out.write(buffer, 0, nBytes);
}
out.flush();
out.close();
in.close();
}
catch (Exception e) {
e.printStackTrace();
}
}

public static void main(String args []){
new ExtractFromJAR().extractMyDBFromJAR(".");
}

}

java -jar mydb.jar