File name utility extracted from FileNameUtils class in Apache's IO library

FileNameUtils.java

/**
 * Simplest utility to fetch the name of file from full path extracted from {@link FileNameUtils} given under below link
 * References : https://android.googlesource.com/platform/packages/apps/UnifiedEmail/+/master/src/org/apache/commons/io/FilenameUtils.java
 */
public class FileNameUtils {

    /**
     * The Unix separator character.
     */
    private static final char UNIX_SEPARATOR = '/';
    /**
     * The Windows separator character.
     */
    private static final char WINDOWS_SEPARATOR = '\\';

    /**
     * Fetches the index of last separator of either UNIX_SEPARATOR or WINDOWS_SEPARATOR
     *
     * @param filename complete filename
     * @return last index of occurrence of either UNIX_SEPARATOR or WINDOWS_SEPARATOR
     */
    private static int indexOfLastSeparator(String filename) {
        if (filename == null) {
            return -1;
        }
        int lastUnixPos = filename.lastIndexOf(UNIX_SEPARATOR);
        int lastWindowsPos = filename.lastIndexOf(WINDOWS_SEPARATOR);
        return Math.max(lastUnixPos, lastWindowsPos);
    }

    /**
     * Gets the name minus the path from a full filename.
     * <p>
     * This method will handle a file in either Unix or Windows format.
     * The text after the last forward or backslash is returned.
     * <pre>
     * a/b/c.txt --> c.txt
     * a.txt     --> a.txt
     * a/b/c     --> c
     * a/b/c/    --> ""
     * </pre>
     * <p>
     * The output will be the same irrespective of the machine that the code is running on.
     *
     * @param filename the filename to query, null returns null
     * @return the name of the file without the path, or an empty string if none exists
     */
    public static String getName(String filename) {
        if (filename == null) {
            return null;
        }
        int index = indexOfLastSeparator(filename);
        return filename.substring(index + 1);
    }
}