Class & Builder - java

Product.java

public class Product {
    private final String prop1;
    private final String prop2;

    private Product(Builder builder) {
        this.prop1 = builder.prop1;
        this.prop2 = builder.prop2;
    }

    // ...

    public static Builder newBuilder() {
        return new Builder();
    }

    public static final class Builder {
        private String prop1="default_1";
        private String prop2="default_2";

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

        public Builder setProp1(String prop1) {
            this.prop1 = prop1;
            return this;
        }

        public Builder setProp2(String prop2) {
            this.prop2 = prop2;
            return this;
        }
    }
}