java - 遍历HashMap [重复](Iterate through a HashMap [duplicate])

Question

This question already has an answer here:

(这个问题已经在这里有了答案：)

• How do I efficiently iterate over each entry in a Java Map?

  (如何有效地遍历Java Map中的每个条目？)

  41 answers

  (41个答案)

What's the best way to iterate over the items in a HashMap ?

(迭代HashMap的项目的最佳方法是什么？)

  ask by burntsugar translate from so

Answer 1

If you're only interested in the keys, you can iterate through the keySet() of the map:

(如果您仅对键感兴趣，则可以遍历地图的keySet() ：)

Map<String, Object> map = ...;

for (String key : map.keySet()) {
    // ...
}

If you only need the values, use values() :

(如果只需要这些值，请使用values() ：)

for (Object value : map.values()) {
    // ...
}

Finally, if you want both the key and value, use entrySet() :

(最后，如果您想要键和值，请使用entrySet() ：)

for (Map.Entry<String, Object> entry : map.entrySet()) {
    String key = entry.getKey();
    Object value = entry.getValue();
    // ...
}

One caveat: if you want to remove items mid-iteration, you'll need to do so via an Iterator (see karim79's answer ).

(一个警告：如果要在迭代中删除项目，则需要通过Iterator进行删除（请参阅karim79的答案 ）。)

However, changing item values is OK (see Map.Entry ).

(但是，更改项目值是可以的（请参见Map.Entry ）。)