### Question:
FilenameUtils { public static String concat(String basePath, String fullFilenameToAdd) { int prefix = getPrefixLength(fullFilenameToAdd); if (prefix < 0) { return null; } if (prefix > 0) { return normalize(fullFilenameToAdd); } if (basePath == null) { return null; } int len = basePath.length(); if (len == 0) { return normalize(fullFilenameToAdd); } char ch = basePath.charAt(len - 1); if (isSeparator(ch)) { return normalize(basePath + fullFilenameToAdd); } else { return normalize(basePath + '/' + fullFilenameToAdd); } } FilenameUtils(); static String normalize(String filename); static String normalize(String filename, boolean unixSeparator); static String normalizeNoEndSeparator(String filename); static String normalizeNoEndSeparator(String filename, boolean unixSeparator); static String concat(String basePath, String fullFilenameToAdd); static String separatorsToUnix(String path); static String separatorsToWindows(String path); static String separatorsToSystem(String path); static int getPrefixLength(String filename); static int indexOfLastSeparator(String filename); static int indexOfExtension(String filename); static String getPrefix(String filename); static String getPath(String filename); static String getPathNoEndSeparator(String filename); static String getFullPath(String filename); static String getFullPathNoEndSeparator(String filename); static String getName(String filename); static String getBaseName(String filename); static String getExtension(String filename); static String removeExtension(String filename); static boolean equals(String filename1, String filename2); static boolean equalsOnSystem(String filename1, String filename2); static boolean equalsNormalized(String filename1, String filename2); static boolean equalsNormalizedOnSystem(String filename1, String filename2); static boolean equals(
            String filename1, String filename2,
            boolean normalized, IOCase caseSensitivity); static boolean isExtension(String filename, String extension); static boolean isExtension(String filename, String[] extensions); static boolean isExtension(String filename, Collection<String> extensions); static boolean wildcardMatch(String filename, String wildcardMatcher); static boolean wildcardMatchOnSystem(String filename, String wildcardMatcher); static boolean wildcardMatch(String filename, String wildcardMatcher, IOCase caseSensitivity); static final char EXTENSION_SEPARATOR; static final String EXTENSION_SEPARATOR_STR; }### Answer:
@Test public void testConcat() throws Exception { assertEquals("src" + File.separator + "test" + File.separator + "java" + File.separator + "nl" + File.separator + "nn" + File.separator + "adapterframework" + File.separator + "util" + File.separator + "test" + File.separator + "test.java", FilenameUtils.concat("src\\test\\java\\nl\\nn\\adapterframework\\util", "test\\test.java")); }