I am having `HashMap` called `testMap` which contains `String, String`.

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

```

When iterating the map, if `value` is match with specified string, I need to remove the key from map.

i.e.

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

```

`testMap` contains `"Sample"` but I am unable to remove the key from `HashMap`.   
Instead getting error :

```
"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)"

```