問題描述

我正在使用 HashMap: byte[] 鍵和字符串值.但我意識到，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，表還是會插入一個新的具有不同HashMapEntry的對象.那么函數(shù) containsKey() 就不能工作了.

into HashMap, the table still inserts a new object with different HashMapEntry. Then function containsKey() cannot work.

有人可以為我解釋一下嗎?我怎樣才能解決這個問題?謝謝.(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;
}

推薦答案

一個 byte[](或任何數(shù)組)不能作為 HashMap，因為數(shù)組不會覆蓋equals，所以兩個數(shù)組只有在引用同一個對象時才會被認為是相等的.

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.

您必須將您的 byte[] 包裝在一些覆蓋 hashCode 和 equals 的自定義類中，并將該自定義類用作HashMap 的關鍵.

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.

這篇關于具有字節(jié)數(shù)組鍵和字符串值的 HashMap - containsKey() 函數(shù)不起作用的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網(wǎng)！