如何在迭代时从HashMap中删除一个键？

Question

我正在HashMap调用testMap哪个包含String, String.

HashMap<String, String> testMap = new HashMap<String, String>();

迭代地图时,if value与指定的字符串匹配,我需要从地图中删除该键.

即

for(Map.Entry<String, String> entry : testMap.entrySet()) {
  if(entry.getValue().equalsIgnoreCase("Sample")) {
    testMap.remove(entry.getKey());
  }
}

testMap包含"Sample"但我无法从中删除密钥HashMap.
而是得到错误:

"Exception in thread "main" java.util.ConcurrentModificationException
    at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
    at java.util.HashMap$EntryIterator.next(Unknown Source)
    at java.util.HashMap$EntryIterator.next(Unknown Source)"

Answer 1

尝试:

Iterator<Map.Entry<String,String>> iter = testMap.entrySet().iterator();
while (iter.hasNext()) {
    Map.Entry<String,String> entry = iter.next();
    if("Sample".equalsIgnoreCase(entry.getValue())){
        iter.remove();
    }
}

使用Java 1.8及更高版本,您只需一行即可完成上述操作:

testMap.entrySet().removeIf(entry -> "Sample".equalsIgnoreCase(entry.getValue()));

Answer 2

使用Iterator.remove().