public static boolean isSub(File parent, File sub) {
		Assert.notNull(parent);
		Assert.notNull(sub);
		return isSub(parent.toPath(), sub.toPath());
	}
@Test
	public void isSubRelativeTest() {
		final File file = new File("..");
		final File file2 = new File(".");
		assertTrue(FileUtil.isSub(file, file2));
	}