hashmapTest | HashMap performance tests from java-performance.info | Performance Testing library

I am using BlueJ and testing the HashMap class to see how it works. Below is the code I used to test the class. There is an error that is thrown in line 23, during the first attempt to call the fillMyMap() method in the constructor.

I tried deleting the call to fillMyMap() in the constructor. The HashMapTester object is instantiated, but the same NullPointerException is thrown when I call that method explicitly.

I tried rewriting the myMap variable declaration, but using a different syntax results in a failure to compile.

I've tested other HashMap code (e.g., from Objects First with BlueJ), and that code runs fine, so there is not a Library, class, or package problem.

I tried changing the variables, thinking I accidentally hit a reserved word. The same result. What is wrong with this code?

I am asking this question with respect to java version till 1.7 only. I am using reflection to find out current capacity of HashMap. In below program am putting 12 unique person into a single bucket of HashMap (using same hashcode) . Then i am putting 13th unique person on same or different bucket(using same or different hashcodes). In both the cases after adding this 13th element, HashMap resizes to 32 buckets. i understand that due to load factor .75 and initial capacity 16 HashMap resizes to it's double with 13th element. But there are still empty buckets available and only 2 buckets are used for these 13th element.

My questions are:

1) Is my understanding correct. Am i not making any mistake. Is this the expected behavior of HashMap .

2) If all this is correct then even though there are 12 or 11 free buckets why the need to double the HashMap with 13th element in this case. Isn't it extra overhead or costly to resize the HashMap. What is the need to double the HashMap in this case While 13th can be put in any avalable bucket according to hashcode.

I am getting a user input from two text fields and storing them into a hash map. I have checked to see if the values are being inserted correctly to the hash map. and they are. once I try to pass it using Intent.putExtra, I am getting this error.