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copied!<p>Two design approaches to consider</p> <p>The <a href="http://www.hillside.net/plop/plop98/final_submissions/P10.pdf" rel="noreferrer">essence</a> pattern</p> <p>The <a href="http://java.dzone.com/news/factories-builders-and-fluent-" rel="noreferrer">fluent interface</a> pattern</p> <p>These are both similar in intent, in that we slowly build up an intermediate object, and then create our target object in a single step.</p> <p>An example of the fluent interface in action would be:</p> <pre><code>public class CustomerBuilder { String surname; String firstName; String ssn; public static CustomerBuilder customer() { return new CustomerBuilder(); } public CustomerBuilder withSurname(String surname) { this.surname = surname; return this; } public CustomerBuilder withFirstName(String firstName) { this.firstName = firstName; return this; } public CustomerBuilder withSsn(String ssn) { this.ssn = ssn; return this; } // client doesn't get to instantiate Customer directly public Customer build() { return new Customer(this); } } public class Customer { private final String firstName; private final String surname; private final String ssn; Customer(CustomerBuilder builder) { if (builder.firstName == null) throw new NullPointerException("firstName"); if (builder.surname == null) throw new NullPointerException("surname"); if (builder.ssn == null) throw new NullPointerException("ssn"); this.firstName = builder.firstName; this.surname = builder.surname; this.ssn = builder.ssn; } public String getFirstName() { return firstName; } public String getSurname() { return surname; } public String getSsn() { return ssn; } } import static com.acme.CustomerBuilder.customer; public class Client { public void doSomething() { Customer customer = customer() .withSurname("Smith") .withFirstName("Fred") .withSsn("123XS1") .build(); } } </code></pre>

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