SequentialExtension is a Java class to create filenames with a sequential extension. Given a directory with file.001, file.002, file.005; what is the next sequential filename? Either file.003 or file.006 - this utility class will return either java.io.File based on your desire for infix mode (file.003) or not (file.006). Get the Java source code for SequentialExtension.java . A utility class for generating sequential file extensions. Assume a directory with: |- file.name.001 |- file.name.002 |- file.name.005 What is the next file name in the sequential set? file.name.006 or maybe file.name.003 Depends on what you want to do. The method nextSequentialFile will generate a File object to meet either need. /* * Copyright (c) 2003 David A. Koontz * Licensed under the Open Software License version 2.0 * http://www.opensource.org/licenses/osl-2.0.php */ import java.io.*; /** * Utility class for generating sequential file extensions. * ...