How to copy objects in Java: Shallow copy and deep copy

When making a copy of an object in Java, there are two types of copies that can be made: shallow copy and deep copy. A shallow copy creates a new instance of the same class as the original object, but it only makes a copy of the references to the objects within the original object. This means that any changes made to the objects referenced by the original object will also affect the copied object.

On the other hand, a deep copy creates a new instance of the same class as the original object and also creates new instances of all the objects referenced by the original object. This ensures that any changes made to the objects referenced by the original object will not affect the copied object.

Shallow copies are useful when we only need to make a copy of an object for temporary purposes, such as passing it to a method or storing it in a collection. However, if we need to modify the copied object without affecting the original object, we must use a deep copy.

To perform a shallow copy in Java, we can use the Object.clone() method. This method creates a new instance of the same class as the original object and only makes a copy of the references to the objects within the original object. To perform a deep copy, we can create a new instance of the same class as the original object and manually copy the values of all the objects referenced by the original object.

It is important to note that when making a copy of an object, we must also ensure that any references to other objects are also copied. This is because if we only copy the references to the objects within the original object, any changes made to those objects will still affect the copied object. To avoid this, we must create new instances of all the objects referenced by the original object when performing a deep copy.

In summary, shallow copies and deep copies are two techniques for making copies of objects in Java. Shallow copies only make a copy of the references to the objects within the original object, while deep copies create new instances of all the objects referenced by the original object. To perform a shallow copy, we can use the Object.clone() method, while to perform a deep copy, we must manually copy the values of all the objects referenced by the original object.