PersonBuilder.java

public static class PersonBuilder {

        private static final Pattern EMAIL_VALIDATION_REGEX = Pattern.compile("^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$");

        private String name;
        private String surname;
        private int age;
        private String email;

        private PersonBuilder() {
        }

        public final PersonBuilder withName(final String name) {
            this.name = name;
            return this;
        }

        public final PersonBuilder withSurname(final String surname) {
            this.surname = surname;
            return this;
        }

        public final PersonBuilder withAge(final int age) {
            this.age = age;
            return this;
        }

        public final PersonBuilder withEmail(final String email) {
            this.email = email;
            return this;
        }

        public final Person build() {
            this.validate();
            return new Person(this.name, this.surname, this.age, this.email);
        }

        private void validate() {
            Objects.requireNonNull(this.name, "The person should have a name");
            Objects.requireNonNull(this.surname, "The person should have a surname");
            Objects.requireNonNull(this.email, "The person should have an email");

            if (this.age <= 0) {
                throw new IllegalArgumentException(String.format("Age should be a positive integer"));
            }

            if (!EMAIL_VALIDATION_REGEX.matcher(this.email).matches()) {
                throw new IllegalArgumentException("Invalid email");
            }
        }
    }