Consider providing static factory methods instead of constructors

Question

The usual way for a class to allow a client to get an instance is to provide a public constructor. Another way to do this is to provide a public static factory method, which is just a static method that returns an instance of the class. What are the pros and cons of using a static factory method?

Answer 1

This chapter in Effective Java explains this well: Consider Static Factory instead of constructors . He explains all the pros and cons for both of them in the best way, as you can understand.

Just to quote the advantages and disadvantages from the book:

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Answer 2

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Answer 3

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Answer 4

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Answer 5

One of the advantages is that you can give the factory methods a friendly name. This will help you easily understand which function works in your function and easily support your code in the future. Take a look at this example, hope this helps you.

    public class Contact {

    private Contact(String displayName, String phoneNumber, int contactType){
    //do something
    }

    //then we will have few functon static to get constructor private
    public static createContactUnknow(String phoneNumber){
        return new Contact("","00000000",0);
    }

    public static createContactValid(String displayName, String phoneNumber, int contactType){
        return new Contact(displayName, phoneNumber, contactType);
    }
}

    //then
    Contact myGirlFriend = Contact.createContactValid("xxxx","000000",1);
    Contact unknowFriend = Contact.createContactUnknow("45454545");