Liskov - violation - hashCode example

PhoneNumber.java

/*
* From Effective Java book - 2nd Edition - Author: Joshua Bloch
*/
public final class PhoneNumber {
       private final short areaCode;
       private final short prefix;
       private final short lineNumber;
       public PhoneNumber(int areaCode, int prefix,
                          int lineNumber) {
           rangeCheck(areaCode,    999, "area code");
           rangeCheck(prefix,      999, "prefix");
           rangeCheck(lineNumber, 9999, "line number");
           this.areaCode  = (short) areaCode;
           this.prefix  = (short) prefix;
           this.lineNumber = (short) lineNumber;
       }
       private static void rangeCheck(int arg, int max,
                                      String name) {
            if (arg < 0 || arg > max)
            throw new IllegalArgumentException(name +": " + arg);
       }
       @Override
       public boolean equals(Object o) { 
            if (o == this)
               return true;
           if (!(o instanceof PhoneNumber))
               return false;
           PhoneNumber pn = (PhoneNumber)o;
           return pn.lineNumber == lineNumber
               && pn.prefix  == prefix
               && pn.areaCode  == areaCode;
       }
   }

Violation.java

Map<PhoneNumber, String> m = new HashMap<PhoneNumber, String>();
m.put(new PhoneNumber(707, 867, 5309), "Jenny");
String result = m.get(new PhoneNumber(707, 867, 5309)) // result = ??