用Java属性文件中的值替换Ha​​shMap键

Question

我必须将基于属性文件映射的HashMap密钥替换为旧的-新的密钥映射。以下方法是替换密钥的最佳方法吗？

KeyMapping.properties

newKey1 oldLKey1
newKey2 oldKey2


//Load property mapping file
ResourceBundle properties = ResourceBundle.getBundle("KeyMapping");

Enumeration<String> newKeys = properties.getKeys();
        Map<String, Object> result = new LinkedHashMap<>();

  while (newKeys.hasMoreElements()) {
    String newKey = (String) newKeys.nextElement();
    Iterator<Entry<String, Object>> iterator = mapToReplaceKeys.entrySet().iterator();

    while(iterator.hasNext()) {
       Entry<String, Object> entry = iterator.next();

      //If key matches the key in property file       
      if (entry.getKey().equals(newKey)) {

      //remove the entry from map mapToReplaceKeys
      iterator.remove();

      //add the key with the 'oldKey' and existing value
      result.put(properties.getString(newKey), entry.getValue());            
    }
  }
}

Answer 1

您本质上是在做什么：

Map<String, Object> result = Collections.list(properties.getKeys())
                .stream()
                .flatMap(element -> mapToReplaceKeys.entrySet()
                        .stream()
                        .filter(entry -> entry.getKey().equals(element)))
                .collect(toMap(e -> properties.getString(e.getKey()),
                        Map.Entry::getValue,
                        (l, r) -> r,
                        LinkedHashMap::new));

或者您也可以这样做：

Map<String, Object> result = new LinkedHashMap<>();
newKeys.asIterator()
       .forEachRemaining(e -> mapToReplaceKeys.forEach((k, v) -> {
             if(k.equals(e)) result.put(properties.getString(k), v);
       }));

Answer 2

不要在Map上进行迭代，只是为了检查密钥是否相等。这就是Map专用查找方法的用途：

ResourceBundle properties = ResourceBundle.getBundle("KeyMapping");
Map<String, Object> result = new LinkedHashMap<>();

for(String newKey: properties.keySet()) {
    Object value = mapToReplaceKeys.remove(newKey);
    if(value != null) result.put(properties.getString(newKey), value);
}

由于要删除映射，因此可以仅在remove上使用Map，这将不执行任何操作，并且在不存在密钥时仅返回null。