I'm using a HashMap: byte[] key and String value. But I realize that even I put the same object (same byte array and same string value) by using
myList.put(TheSameByteArray, TheSameStringValue)
into HashMap, the table still inserts a new object with different HashMapEntry. Then function containsKey() cannot work.
Can someone explains this for me? How can I fix this? Thanks. (Android Java)
@Override public boolean containsKey(Object key) {
if (key == null) {
return entryForNullKey != null;
}
int hash = Collections.secondaryHash(key);
HashMapEntry<K, V>[] tab = table;
for (HashMapEntry<K, V> e = tab[hash & (tab.length - 1)];
e != null; e = e.next) {
K eKey = e.key;
if (eKey == key || (e.hash == hash && key.equals(eKey))) {
return true;
}
}
return false;
}
A byte[]
(or any array) can't work properly as a key in a HashMap
, since arrays don't override equals
, so two arrays will be considered equal only if they refer to the same object.
You'll have to wrap your byte[]
in some custom class that overrides hashCode
and equals
, and use that custom class as the key to your HashMap.