Java：遍历另一个 HashMap 中的 HashMap
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/31242039/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Java: Iterate through a HashMap which is inside another HashMap
提问by Chanuka Ranaba
I want to iterate through a HashMapwhich is inside another HashMap
我想遍历HashMap另一个内部的aHashMap
Map<String, Map<String, String>> PropertyHolder
I was able to iterate through the parent HashMapas following,
我能够HashMap按如下方式遍历父级，
Iterator it = PropertyHolder.entrySet().iterator();
while (it.hasNext()) {
Map.Entry pair = (Map.Entry) it.next();
System.out.println("pair.getKey() : " + pair.getKey() + " pair.getValue() : " + pair.getValue());
it.remove(); // avoids a ConcurrentModificationException
}
but could not able to iterate through the child Map, It can be done by converting pair.getValue().toString()and separated using ,and =. Is there any other way of iterating it?
但无法遍历子代Map，可以通过pair.getValue().toString()使用,and转换和分隔来完成=。有没有其他迭代方法？
采纳答案by seanhodges
You could iterate the child map similar to how you've done the parent:
您可以迭代子映射类似于您完成父级的方式：
Iterator<Map.Entry<String, Map<String, String>>> parent = PropertyHolder.entrySet().iterator();
while (parent.hasNext()) {
Map.Entry<String, Map<String, String>> parentPair = parent.next();
System.out.println("parentPair.getKey() : " + parentPair.getKey() + " parentPair.getValue() : " + parentPair.getValue());
Iterator<Map.Entry<String, String>> child = (parentPair.getValue()).entrySet().iterator();
while (child.hasNext()) {
Map.Entry childPair = child.next();
System.out.println("childPair.getKey() : " + childPair.getKey() + " childPair.getValue() : " + childPair.getValue());
child.remove(); // avoids a ConcurrentModificationException
}
}
I've presumed you want to call .remove()on the child map, which will lead to a ConcurrentModificationException if done while looping the entrySet - it looks as though you discovered this already.
我假设您想调用.remove()子映射，如果在循环 entrySet 时完成，这将导致 ConcurrentModificationException - 看起来好像您已经发现了这一点。
I've also swapped out your use of casting with strongly-typed generics as suggested in the comments.
我还按照评论中的建议，将您对强类型泛型的使用换掉了。
回答by griFlo
for (Entry<String, Map<String, String>> entry : propertyHolder.entrySet()) {
Map<String, String> childMap = entry.getValue();
for (Entry<String, String> entry2 : childMap.entrySet()) {
String childKey = entry2.getKey();
String childValue = entry2.getValue();
}
}
回答by duffymo
It's obvious - you need two nested loops:
很明显 - 您需要两个嵌套循环：
for (String key1 : outerMap.keySet()) {
Map innerMap = outerMap.get(key1);
for (String key2: innerMap.keySet()) {
// process here.
}
}
