What other types of indexes do you know besides B-tree?

In addition to B-trees, there are other types of indexes used in databases and Java applications:

• Hash indexes — provide quick access by exact key match but do not support range queries.
• Bitmap indexes — effective for columns with low cardinality (e.g., gender, status).
• R-tree — used for spatial data, such as geographic coordinates.
• GiST (Generalized Search Tree) — a generalized structure for various data types.
• Full-text indexes — for fast text search.

In Java, data structures from collections or specialized libraries can be used to implement indexes, such as HashMap (hash index), TreeMap (red-black tree, similar to B-tree).