code: public static final File[] findJarFileByDir(File dir)
  	{
  		if(dir==null)
  		{
  			throw new NullArgumentException("dir ==null");
  		}
  		if(dir.isFile())
  		{
  			throw new IllegalArgumentException("dir "+dir+" is not a dir");
  		}
  		if(!dir.exists())
  		{
  			throw new IllegalArgumentException("dir "+dir+" not found");
  		}
  		File[] jarFiles = dir.listFiles(new FileFilter() {
  			@Override
  			public boolean accept(File pathname) 
  				{
  					return pathname.getName().endsWith(".jar");
  				}
  			});
  		return jarFiles;
  	}
docs: 寻找目录下面的jar
  @param dir
  @return