The wwPDB will run out of 4-character PDB IDs soon and will switch to an extended format: https://www.wwpdb.org/news/news?year=2021#607760112786e73a79c76f9d

The new format will be eight characters prefixed by ‘PDB’, e.g., pdb_00001abc.

Chemical compounds will also run out of 3-letter identifiers soon and will switch to 4-letter identifiers. These are incompatible with the PDB file format.

We should ensure that biojava parsers, data structures, and algorithms can handle both of these changes.