具有字节数组键和字符串值的 HashMap - containsKey() 函数不起作用
我正在使用 HashMap: byte[] 键和字符串值.但我意识到，即使我使用
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)
到HashMap中，表还是会插入一个新的具有不同HashMapEntry的对象.那么函数 containsKey() 就不能工作了.
into HashMap, the table still inserts a new object with different HashMapEntry. Then function containsKey() cannot work.
有人可以为我解释一下吗?我怎样才能解决这个问题?谢谢.(Android Java)
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;
}
推荐答案
一个 byte[](或任何数组)不能作为 HashMap，因为数组不会覆盖equals，所以两个数组只有在引用同一个对象时才会被认为是相等的.
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.
您必须将您的 byte[] 包装在一些覆盖 hashCode 和 equals 的自定义类中，并将该自定义类用作HashMap 的关键.
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.
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