/**
 * A record class for representing names.  A name consists of a
 * first name and a last name.  However, to accommodate people
 * who use only one name, the last name can be null.
 */
public record FullName(String firstName, String lastName) {

    /**
     * Canonical constructor takes two parameters representing
     * the first name and the last name.  The last name can be 
     * null, but if the first name is null an IllegalArgumentException
     * will be thrown.
     */
    public FullName {
        if (firstName == null) {
            throw new IllegalArgumentException("First name can't be null.");
        }
    }
    
    /**
     * Constructor for creating a FullName for a person who uses
     * only one name.  The parameter represents that name, which 
     * becomes the firstName field of the FullName.  The lastName
     * field is null.
     */
    public FullName(String name) {
        this(name,null);
    }
    
    /**
     * For a person who uses only one name, returns that name.
     * Otherwise, returns a string containing the first name
     * and the last name, separated by a space.
     */
    public String toString() {
        if (lastName == null)
            return firstName;
        else
            return firstName + " " + lastName;
    }
    
    /**
     * Returns true if this FullName is the name of a person
     * who uses only one name.
     */
    public boolean oneNameOnly() {
        return lastName == null;
    }
    
} // end record FullName