private static <K, V> void copyMapEntries(Map<K, V> destMap,
                                              Map<K, ? extends V> srcMap,
                                              Set<K> keySet) {
        for (K k : keySet) {
            copyMapEntry(destMap, srcMap, k);
        }
    }
Copy entries from one map into another.

@param destMap   The map to copy entries into.
@param srcMap    The map to copy entries from.
@param keySet    Only entries with these keys will be copied.
@param <K>       The map key type.
@param <V>       The map value type.
clients/src/main/java/org/apache/kafka/common/security/ssl/SslFactory.java