JB Renamer (Java Batch Renamer) is my open source (GNU LGPL v3) tool to batch rename files.
Main features:
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1. Add sequence to file name
2. Re-sequence the file name, eg. change the digits of existing sequences
3. Replace part of the file name either literally or by regular expression (Java style)
4. Move part of the file name
5. Test renaming without the real name change
6. Unlimited undo/redo
7. Save file names in a directory to a text file
8. Pre-defined renaming: load a file list to rename
System Requirements:
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Java 1.6
Download it here.
Website and Source code