Java hashmap key value iterator

Question

I have a hashmap when i am printing this hashmap the output is like this

{KEY_CH_UP=KEY_CH_UP, KEY_PANEL_CH_UP=KEY_PANEL_CH_UP, KEY_7=KEY_7, KEY_6=KEY_6, KEY_5=null}

Now i want to get all the keys which is having

values == null ;

and what have you tried to get what you want? Read whathaveyoutried.com — jlordo
– jlordo, Commented Jan 9, 2013 at 11:07
@GauravSakhardande: I agree, great blog. But I'm not the author ;) — jlordo
– jlordo, Commented Jan 9, 2013 at 11:10
I do not see how Java EE is relevant here. HashMap is a part of standard Java SE. Retaging. — Audrius Meškauskas
– Audrius Meškauskas, Commented Jan 9, 2013 at 11:23

PermGenError · Accepted Answer · 2013-01-09 11:08:16Z

4

Iterate over the like below and check if the value is null :

Map<String, String> map = new HashMap<String, String>();
        for(Map.Entry<String, String> en: map.entrySet()){
            if(en.getValue()==null){
                System.out.println(en.getKey());
            }
        }

answered Jan 9, 2013 at 11:08

PermGenError

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1 Comment

Peter Lawrey Over a year ago

+1 Basically the OP is searching a Map by value. It doesn't have a more efficient way of doing this than iterating over every value which is why searching by value could indicate a poor design choice.

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