title: abstract compareTo method not being overrided
body: <p>When compiling the code below, I get the following error: </p>
  
  <blockquote>
    <p>PersonalInformation is not abstract and does not override abstract
    method compareTo(Object) in Comparable</p>
  </blockquote>
  
  <p>I assume that means I have a problem with my <code>compareTo</code> method. But everything seems to be all right. Anyone have a suggestion?</p>
  
  <pre><code>import java.util.*;
  public class PersonalInformation implements Comparable
  {
  private String givenName;
  private String middleInitial;
  private String surname;
  private String gender;
  private String emailAddress;
  private String nationalId;
  private String telephoneNum;
  private String birthday;
  
  public PersonalInformation(String gN, String mI, 
          String sur, String gen, String eMa, String natId,
          String teleNum, String birthd)
  
  {
          givenName = gN;
          middleInitial = mI;
          surname = sur;
          gender = gen;
          emailAddress = eMa;
          nationalId = natId;
          telephoneNum = teleNum;
          birthday = birthd;
  
  
  }
  
  
  public int compareTo(PersonalInformation pi)
  {
   return (this.gender).compareTo(pi.gender);
  }
  
  }
  </code></pre>