# About Type Maps

A type map matches Java datatypes to SQL types. For example, see the following table.

Java | SQL
`Boolean` | `BIT`
`Float` | `REAL`
`Long` | `BIGINT`
`java.math.BigDecimal` | `NUMERIC`
`java.sql.Date` | `DATE`

Business Components for Java contains two type maps:

- Oracle - Database columns are mapped to oracle.jbo.domain types

- Java - Database columns are mapped to Java types

If you are using a foreign datasource you may need to customize the type map to adequately describe the mapping of the data in your database to their corresponding Java formats.

To view the Java type map class, see The Java Type Map Class.

Note: You must choose a type map before generating business components, you cannot change it afterwards.