The nested builder patterns that I've come across online usually have something like this:
class Person{
private int id;
private String name;
private int age;
... so on
private Person(Builder builder){
this.id = builder.id;
this.name = builder.name;
this.age = builder.age;
}
public static class Builder{
private int id;
private String name;
private int age;
... so on
public Builder id(int id){
this.id = id;
return this;
}
public Builder name(String name){
this.name = name;
return this;
}
.... so on
public Person build(){
return new Person(this);
}
}
}
My question is, is it necessary to duplicate fields in Person and Builder? It seems like a lot of redundant code. And my second question is, would the following code be a viable replacement, why or why not?
class Person{
private int id;
private String name;
private int age;
... so on
private Person(){}
public static class Builder{
private Person person = new Person();
public Builder id(int id){
this.person.id = id;
return this;
}
public Builder name(String name){
this.person.name = name;
return this;
}
.... so on
public Person build(){
return person;
}
// UPDATED -- another build method
public Person build(){
Person built = this.person;
this.person = new Person();
return built;
}
}
}
Note: I understand this topic may be opinionated and there may not be a "right" answer, but I just want to hear different ideas and opinions. I'm not looking for the ultimate truth.