CODEWITHSUNDEEP
hashmap
molamola
molamola

Reputation: 269

Why customized getkey() function is not working in java?

I made getKey() function to get a key from HashMap<ArrayList<String>,String> variable.

But It is not working, I totally don't know why it is not working.

private ArrayList<String> getKey(String value) {
        Iterator<ArrayList<String>> it=history_map.keySet().iterator();
        while(it.hasNext()) {
            if(history_map.get(it.next()).equals(value)) {
                return it.next();
            }
        }
        return null;
    }

value is "Function". and history_map has key type ArrayList<String>.

So I find value comparing every value of key. What is the problem?

It always return null value.

I use this function in below.

public void setFunction(String function) {
        getKey("Function").add(function);
    }
    public void setEnergyLevel(int energy) {
        getKey("EnergyLevel").add(String.valueOf(energy));
    }
    public void setTemperature(int temp) {
        getKey("Temperature").add(String.valueOf(temp));
    }
    public void setHumidity(int hum) {
        getKey("Humidity").add(String.valueOf(hum));
    }
    public void setSpeed(int speed) {
        getKey("Fastest speed").add(String.valueOf(speed));
    }

Upvotes: 0

Views: 264

Answers (1)

Shailesh Pratapwar
Shailesh Pratapwar

Reputation: 4224

One reason could be inside the if:

if(history_map.get(it.next()).equals(value)) {
      return it.next();
}

If the match is found, iterators next() method is called again while executing return statement. If map consist of single key, then it will throw java.util.NoSuchElementException.

Upvotes: 1

Related Questions