You can use a DatabaseMetaData object to obtain information about the database as a whole as well as catalog information.
The following example shows how to return a list of tables, which is a catalog function:
// Connect to the server.
Connection c = DriverManager.getConnection("jdbc:as400://mySystem");
// Get the database metadata from the connection.
DatabaseMetaData dbMeta = c.getMetaData();
// Get a list of tables matching the following criteria.
String catalog = "myCatalog";
String schema = "mySchema";
String table = "myTable%"; // % indicates search pattern
String types[] = {"TABLE", "VIEW", "SYSTEM TABLE"};
ResultSet rs = dbMeta.getTables(catalog, schema, table, types);
// Iterate through the ResultSet to get the values.
// Close the Connection.
c.close();