section in an unordered dictionaryhoweverno order relation is assumed on the keyshenceonly equality testing between keys is used as an adtan (unordereddictionary supports the following methodssize()return the number of entries in isempty()test whether is empty find( )if contains an entry with key equal to kthen return such an entryelse return null findall( )return an iterable collection containing all entries with key equal to insert( , )insert an entry with key and value into dreturning the entry created remove( )remove from an entry ereturning the removed entry or null if was not in entries()return an iterable collection of the key-value entries in notice that our dictionary operations use entrieswhich are the key-value pairs stored in the dictionary we assume each entry comes equipped with getkey(and getvalue(methods to access its key and value components respectively when the method find(kis unsuccessful (that isthere is no entry with key equal to )we use the convention of returning sentinel null another choiceof coursewould be to throw an exception for an unsuccessful find( )but that would probably not be an appropriate use of an exceptionsince it is normal to ask for key that might not be in our dictionary moreoverthrowing and catching an exception is typically slower than test against sentinelhenceusing sentinel is more efficient note thatas we have defined ita dictionary can contain different entries with equal keys in this caseoperation find(kreturns an arbitrary entry ( , )whose key is equal to we mentionin passingthat our dictionary adt should not be confused with the abstract class java util dictionarywhich actually corresponds to the map adt given above and is now considered obsolete example in the followingwe show series of operations on an initially empty dictionary storing entries with integer keys and character values operation output