Java – the key in treemap returns null

So I have a very strange mistake When I first used keyset () to iterate over the first 10 keys of a large treemap, I stumbled upon it One of the keys is to return null, which is impossible as far as I understand So I wrote the test code below:

int i = 0;
        for (Map.Entry<String,Integer> es : sortedMap.entrySet()){
            if (i >= 10) {
                break;
            }

            if (sortedMap.containsKey(es.getKey())){
                System.out.println(es.getKey() + ":" + sortedMap.get(es.getKey()));
            } else {
                System.out.println("Key " + es.getKey() + " does not exist,yet...");
                System.out.println("This does work: " + es.getKey() + ":" + es.getValue());
                System.out.println("This does NOT work: " + es.getKey() + ":" + sortedMap.get(es.getKey()));
            }
            i++;
        }

The following results were obtained:

SOAP:967
'excerpt'::679
'type'::679
Key 'author_url': does not exist,yet...
This does work: 'author_url'::679
This does NOT work: 'author_url'::null
'date'::679
Android:437
TLS:295
message:283
server:230
monthly:215
<<<<<<<<<<<<<<<<<<<<DUMPING MAP!
{SOAP=967,'excerpt':=679,'type':=679,'author_url':=679,'date':=679,Android=437,TLS=295,message=283,server=230,monthly=215...

I cut off the map after the top ten because there are more maps, but all these are a valuable key

So my question is: why do I get null when I use the key to get the key directly from treemap, but the entryset returns the correct key and value?

This is my comparator because I ordered it on integer:

class ValueComparator implements Comparator<Object> {

  Map<String,Integer> base;
  public ValueComparator(Map<String,Integer> base) {
      this.base = base;
  }

  public int compare(Object a,Object b) {

    if ((Integer) base.get(a) < (Integer) base.get(b)) {
      return 1;
    } else if ((Integer) base.get(a) == (Integer) base.get(b)) {
      return 0;
    } else {
      return -1;
    }
  }
}

The construction of treemap is as follows:

ValueComparator bvc =  new ValueComparator(allMatches);
TreeMap<String,Integer> sortedMap = new TreeMap<String,Integer>(bvc);
//Sort the HashMap
sortedMap.putAll(allMatches);

Allmatches is HashMap < string, integer >

Solution

As can be seen from the iteration order displayed in treemap, you are using a custom comparator [otherwise, iterations will be arranged in dictionary order]

Note that according to JavaDocs:

If your comparator does not apply these rules – the behavior is undefined and may display strange results – as you can see

Edit: [in response to an edit question] your quarantine uses identity [operator =] to check two integers Note that integer is an object – so operator = = returns true only if it is the same object You should use equals () to check that two integers are the same – or even better – using integer compareTo()