Java

The method enlargeHashTable does not retain the instances of Entry that were in the old hash table. It could if the method add had an entry as its parameter instead of the search key and value. Write such a method as an additional but private add method, and then revise enlargeHashTable so it retains the instances of Entry that were in the old hash table.

$//$ Old add method:

public V add$($K key, V value$)\{$

if $(($key $==$ null$)||($value $==$ null$))\{$

throw new NoSuchElementException$("$Key or value not found."$)$;

$\}$

int index $=$ getHashIndex$($key$)$;

V oldValue;

if $(!$contains$($key$))\{$

hashTable$[$index$]=$ new Entry$($key$,$ value$)$;

numberOfEntries$++$;

oldValue $=$ null;

$\}$ else $\{$

oldValue $=$ hashTable$[$index$].$getValue$()$;

hashTable$[$index$].$setValue$($value$)$;

$\}$

if $($isHashTableTooFull$())\{$

enlargeHashTable$()$;

$\}$

return oldValue;

$\}$

private void enlargeHashTable$()\{$

Entry$[]$ oldTable $=$ hashTable;

int oldSize $=$ hashTable.length;

int newSize $=$ getNextPrime$($oldSize $+$ oldSize$)$;

checkSize$($newSize$)$;

Entry$[]$ temp $=($Entry$[])$ new Entry$[$newSize$]$;

hashTable $=$ temp;

numberOfEntries $=0$;

for $($int index $=0$; index $<$ oldSize; index$++)\{$

if $(($oldTable$[$index$]!=$ null$)$ && $($oldTable$[$index$]!=$ AVAILABLE$))\{$

add$($oldTable$[$index$].$getKey$(),$ oldTable$[$index$].$getValue$())$;

$\}//$ end for

$\}//$ end enlargeHashTable

$\}$