Java: Difference between initializing by constructor and by static method?

Question

This might just be a question of personal taste and workflow, but in case it\'s more than that, I feel I should ask anyway.

In Java, what differences are there betwe

Answer 1

The difference is a static factory method is more flexible. It can have all sorts of ways to return an instance. It can do other side stuff. It can have a more descriptive name. It can be invoked by its simple name (e.g. foo(args)) by static import or inheritance.

The constructor call is more certain - the caller knows exactly what's happening - a new instance of that exact class is created.

Answer 2

There are both advantages and disadvantages of static factory methods.

Advantages

• Descriptive, meaningful names.
• When invoked they can decide whether to return a new instance
• They can return an object of any subtype of the return type
• They reduce the verbosity of creating parameterized type instances

Disadvantages

• If you provide only static factory methods, classes without public or protected constructors cannot be subclassed
• They are not readily distinguishable from other static methods

Source: Effective Java, Second Ed.