Parallel stacking method

Here are a few examples of "Builder", if you don't understand, that's your problem. Practice more again.

public class Person {
    private final int id;
    private final String name;
    private final int age;

    public static class Builder {
        private String name;
        private int id  = 0;
        private int age = 0;

        public Builder(String name) {
            this.name = name;
        }

        public Builder age(int age) {
            age = age;
            return this;
        }

        public Builder id(int id) {
            id = id;
            return this;
        }

        public Person build() {
            return new Person(this);
        }
    }

    public Person(Builder builder) {
        this.id   = builder.id;
        this.name = builder.name;
        this.age  = builder.age;
    }

    public static void main(String[] args) {
        Person person = new Builder("test")
                .age(23).id(2).build();
    }
}

public abstract class Pizza {

    public enum Topping {HAM, MUSHROOM, ONION, PEPPER, SAUSAGE}
    final Set<Topping> toppings;

    abstract static class Builder<T extends Builder<T>> {
        EnumSet<Topping> toppings = EnumSet.noneOf(Topping.class);

        public T addTopping(Topping topping) {
            toppings.add(Objects.requireNonNull(topping));
            return self();
        }

        protected abstract T self();

        abstract Pizza build();
    }
    Pizza(Builder<?> builder) {
        toppings = builder.toppings.clone();
    }

}

public class NyPizza extends Pizza {
    public enum Size {SMALL, MEDIUM, LAGER}
    private final NyPizza.Size size;

    public static class Builder extends Pizza.Builder<NyPizza.Builder> {
        private final Size size;

        public Builder(NyPizza.Size size) {
            this.size = Objects.requireNonNull(size);
        }

        @Override
        public NyPizza build() {
            return new NyPizza(this);
        }

        protected Builder self() {
            return this;
        }
    }

    private NyPizza(Builder builder) {
        super(builder);
        size = builder.size;
    }
}

I think you'd better learn the second example, although the first example is enough to express this usage clearly.

Finally, I hope you can see the equal sign alignment in the first example and use this style.