Then you want to use the toString() or some getValue() method to get at the required attribute of Counter: In fact, toString() was being called implicitly by the original code:
pw.println(me.getKey()+":"+"\t"+((Counter)me.getValue()));
String concatenation (+) on an Object automatically invokes toString() if the Object is not already a String. So you may find it useful to add a toString() method to your Counter class which gives you the desired output:
Now anytime you include a Counter object in a print statement, it will convert to a meaningful String rather than the ugly serial-number-type thing which you inherit by default from the Object class.