Null pointer exception error while using Hashmap

Asked Jun 13 '15 at 15:37

Active Jun 13 '15 at 15:37

Viewed 18 times

public void method(int a[], int len, int x)
{
    Map<Integer, Integer> map = new HashMap<Integer, Integer>();

    for(int i=0;i<len;i++)
    {
        System.out.println(i);
        int temp = x-a[i];
        System.out.println(temp);
        if(temp>=0 && map.get(temp) ==1)
        {
            System.out.println(temp+" "+a[i]);
        }
        else
        {
            map.put(a[i],1);
        }
    }
}

java.lang.NullPointerException is occurring on line no. 9. How to remove this???

asked Jun 13 '15 at 15:37

user3654181

Which line is line no. 9? – Hovercraft Full Of Eels Jun 13 '15 at 15:38
1

Note the general concepts of how to debug a NPE (NullPointerException): **You should critically read your exception's stacktrace to find the line of code at fault, the line that throws the exception, and then inspect that line carefully**, find out which variable is null, and then trace back into your code to see why. You will run into these again and again, trust me. – Hovercraft Full Of Eels Jun 13 '15 at 15:38
The line no. 9 is --- if(temp>0 && map.get(temp) ==1) – user3654181 Jun 13 '15 at 15:39
1

Then I'd guess that there is no value associated to the `temp` key in your map. – mastov Jun 13 '15 at 15:39
You're calling `get(...)` before filling data into the map. Check for null first. `if (map.get(temp) == null) {...}` – Hovercraft Full Of Eels Jun 13 '15 at 15:40

Null pointer exception error while using Hashmap

0 Answers0