Prototype

Prototype Pattern (Creational)

Creates objects by cloning an existing object

Problem

Application need to know the class of objects already created to create more using new.

Solution

Let objects to create others from themselves using a clone method.

Create a factory object to maintain the initial instances

Considerations

• Prototype can avoid expensive "creation from scratch"
• Let client to create objects without know the type
• Rules for method clone in JVM:
  1. x.clone() != x will be true
  2. x.clone().getClass() == x.getClass() will be true, but these are not absolute requirements.
  3. x.clone().equals(x) will be true, this is not an absolute requirement.

Related patterns

• Singleton avoids the creation of multiple instances. Prototype return a new instance in every call.
• Factory method: creation through inheritance. Prototype: creation through delegation

References

• https://sourcemaking.com/design_patterns/prototype
• https://www.tutorialspoint.com/design_pattern/prototype_pattern.htm
• http://howtodoinjava.com/core-java/cloning/a-guide-to-object-cloning-in-java/