Under what scenario entry returned by map.entrySet is NULL ?

[Sunni srivastav]

I came across a code snippet which iterates over a map using its entry set and performs some action only if entry != null

As far as I know even if we don't enter anything in map this method returns an empty set and not a null set.
Even if I put {null,null} then the entry will be [null,null] employing an instance of set with these elements.

Map<String, String> map = new HashMap<String, String>();
		map.put(null, null);
		map.put(string1, string1);
		for(Map.Entry<String, String> entry : map.entrySet()){
			if(entry != null){
                                  //do something
			}
			
		}

I have below question:
1. Under what scenario an entry in HashMap will it be NULL?
2. Is the check even valid ?

[Jesper de Jong]

This never happens; the person who wrote that code was mistaken, or overly concerned about NullPointerExceptions.

The null check is redundant and can be removed without any change in functionality.

[Matthew Brown]

It's possible in a HashMap for the key or value to be null. So doing this may make sense in some circumstances:

for(Map.Entry<String, String> entry : map.entrySet()){
    if(entry.getKey() != null){
        ....
    }
}

for(Map.Entry<String, String> entry : map.entrySet()){
    if(entry.getValue() != null){
        ....
    }
} 

But as Jesper says, the Entry itself will never be null.