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copied!<p>If you want to set several variables at once just define a function:</p> <pre><code>public class Person { public Person(String firstName, String lastName, Date dateOfBirth) { set(firstName, lastName, dateOfBirth); } public void set(String firstName, String lastName, String dateOfBirth) { ... } } </code></pre> <p>By definition an object is only constructed once, hence the constructor is only called once.</p> <p>One thing worth noting: it's more common to favour immutability, so:</p> <pre><code>public class Person { private final String firstName; private final String lastName; private final Date dateOfBirth; public Person(String firstName, String lastName, Date dateOfBirth) { this.firstName = firstName; this.lastName = lastName; this.dateOfBirth = dateOfBirth == null ? null new Date(dateOfBirth.getTime()); } public String getFirstName() { return firstName; } public String getLastName() { return lastName; } public Date getDateOfBirth() { return dateOfBirth == null ? null : new Date(dateOfBirth.getTime()); } public Person withFirstName(String firstName) { return new Person(firstName, lastName, dateOfBirth); } public Person withLastName(String lastName) { return new Person(firstName, lastName, dateOfBirth); } public Person withDateOfBirth(Date dateOfBirth) { return new Person(firstName, lastName, dateOfBirth); } } </code></pre> <p>because a lot of concurrency issues simply go away when you do this. Not just concurrency issues too. <code>String</code>, <code>BigDecimal</code>, <code>BigInteger</code> and some other standard classes are immutable (immutable means once instantiated its state can never change). <code>Date</code> isn't. You see in the above code I have to constantly defensively copy the date of birth? That's because <code>Date</code> is not immutable. If you didn't a caller could do this:</p> <pre><code>public class Person { private final Date dateOfBirth; ... public Date getDateOfBirth() { return dateOfBirth; } } Person person = new Person(...); Date date1 = person.getDateOfBirth(); date1.setTime(1000000000L); System.out.println(person.getDateOfBirth()); </code></pre> <p>The date of birth will have changed. That problem is caused solely by <code>Date</code> being mutable. That's another reason to favour immutability.</p>

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