What is Connector made by java and xml code in sailpoint? Please explain use of it in detail?

When there is no OutOfTheBox (OOTB) connector to fulfill your requirements, you can create a custom connector.

There is hardly any need to create a custom connector, as there are many connectors available for IdentityIQ:
https://documentation.sailpoint.com/connectors/identityiq/landingpage/landingpages/identityiq_connectivity_landing.html

– Remold