具有字节数组键和字符串值的 HashMap - containsKey

问题描述

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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