Answer 1

Composite, the word itself means that it is a combination or a mixture. The composite data types could be arrays, lists etc. in Java.

On the other hand, user defined data types in general are classes and interfaces in Java which we create according to our convenience.

Answer 2

Composite data types are derived from primitive data types. For example arrays. On the other hand User defined data types are those that user / programmer himself defines. For example, classes, interfaces.

Answer 3

ℕ𝕚𝕝𝕖𝕤𝕙 𝕂𝕒𝕟𝕥𝕚[#Happy Coding😄] In java programming user defined datatype can be developed by using the features of classes and interfaces.

Whereas in other languages like In C/C++ , user defined data types can be developed by using struct, union, enum etc.