Here is the PrincipalImpl we'll use in this tutorial.

import java.io.Serializable;
import java.security.Principal;

//
// This class defines the principle object, which is just an encapsulated 
// String name 
public class PrincipalImpl implements Principal, Serializable {

     private String name;

     public PrincipalImpl(String n) {
       name = n;
     }

     public boolean equals(Object obj) {
       if (!(obj instanceof PrincipalImpl)) {
         return false;
       }
       PrincipalImpl pobj = (PrincipalImpl)obj;
       if (name.equals(pobj.getName())) {
         return true;
       }
       return false;
     }

     public String getName() {
       return name;
     }

     public int hashCode() {
       return name.hashCode();
     }

     public String toString() {
       return getName();
     }

}