What is the difference between deep copy and shallow copy in Java?

In Java, deep copy and shallow copy refer to whether reference types inside an object are also copied during the copying process.

Shallow copy: A shallow copy only duplicates the object’s reference, rather than creating a completely new object. The copied object and the original object will both share the same reference type data, so modifying the reference type data of one object will affect the other object.

Deep copy: Deep copy creates a completely new object and copies all values and reference type data from the original object. The copied object and the original object do not share reference type data, so modifying the reference type data in one object will not affect the other object.

In short, shallow copy only duplicates references, while deep copy duplicates all data.