Shallow Copy

A shallow copy generates a new object by merely copying the references to the old object’s fields.

This indicates that the original and cloned objects contain the same underlying data.

Any changes made to the duplicated item will also affect the original object.

When to use shallow copy

Use when you need a fast copy of an object and are confident that changing the duplicate will not damage the original.

For example, copying immutable objects or objects without modified fields.

Deep Copy

A deep copy produces a new object by recursively copying all fields, including objects within it.

This assures that the cloned item is fully separate from the original object.

Any modifications made to the duplicated item will not impact the original.

When to use deep copy

You can use deep copy when you want an entirely separate clone of an object and want to change it without impacting the original.

For example, copying complex objects with nested mutable fields or when passing objects to different threads.

Note: Java’s clone() function usually makes a shallow copy. To do a deep copy, you must frequently modify the clone() function and write deep copying logic for all changeable fields.