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HashMap Help?!

 
Greenhorn
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How would you check that a given key corresponds to a given object (if you stored an Object)?
And how would, given a specific key, retrieve the corresponding details of that Object?
Eg: if i have a Person with String fname, String lname, String ID (and methods to return those Strings)
in :
HashMap hm = new HashMap();
Person person = new Person();
hm.put(person.ID(), person);
How would I retrieve corresponding String fname given a specific ID??
 
Ranch Hand
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Person person = (Person) hm.get(id);
String fname = person.fname();
or, in one line:
String fname = ((Person) hm.get(id)).fname();
 
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