如何覆盖 HashMap 的 putAll 以在每个 <K,V> 对上调用 put？

Question

我正在尝试覆盖 PutAll 以循环遍历这些对并在它们上调用 put，因为我使用的是自定义 HashMap 对象。我试过这个：

        @Override
        public void putAll(final Map m) {
            Iterator iterator = m.entrySet().iterator();
            while (iterator.hasNext()) {
                Map.Entry pairs = (Map.Entry)iterator.next();
                put(pairs.getKey(), pairs.getValue());
            }
        }

但它给了我以下错误：

Compiling the source code....
$javac HelloWorld.java 2>&1
HelloWorld.java:109: error: no suitable method found for put(Object,Object)
                put(pairs.getKey(), pairs.getValue());
                ^
    method UniqueHashMap.put(K,V) is not applicable
      (actual argument Object cannot be converted to K by method invocation conversion)
    method HashMap.put(K,V) is not applicable
      (actual argument Object cannot be converted to K by method invocation conversion)
    method AbstractMap.put(K,V) is not applicable
      (actual argument Object cannot be converted to K by method invocation conversion)
  where K,V are type-variables:
    K extends Object declared in class UniqueHashMap
    V extends Object declared in class UniqueHashMap
1 error

Answer 1

不要用Raw Types，你好像有泛型K,V这样用，

@Override
public void putAll(Map<? extends K, ? extends V> m) {
  Iterator<? extends K> iterator = m.keySet().iterator();
  while (iterator.hasNext()) {
    K key = iterator.next();
    put(key, m.get(key));
  }
}

Answer 2

我猜你的自定义地图类有类型参数，所以你正确的覆盖应该是：

@Override
void putAll(Map<? extends K,? extends V> m) {
  Iterator<Map.Entry<? extends K,? extends V>> iterator = m.entrySet().iterator();
  while (iterator.hasNext()) {
    Map.Entry<? extends K,? extends V> pairs = iterator.next();
    put(pairs.getKey(), pairs.getValue());
  }
}

其中K 和V 是用于您的类的类型变量。