When using custom Java indexing code, the following best practices will make your life easier:

• Create small classes containing related functionality for ease of maintenance. SolrMarc will find and compile all of the classes that you place under the import/index_java directory under your $VUFIND_HOME and $VUFIND_LOCAL_DIR.
• Use distinctive method names; if you have the same method name in multiple classes, you will have to disambiguate the class name in your marc.properties file. Using distinctive names makes the shorthand syntax more reliable.
• If your custom code needs to access public methods from the core SolrIndexer class, use SolrIndexer.instance() to reach them.
• If your custom code needs to cache or persist values, create a thread-safe singleton to encapsulate those values. You can see an example of this pattern in the ConfigManager used by, among other things, the FullTextTools.