Question

In my code I am trying to get if a number exist in the hashmap or not. My code is following:

BitSet arp = new BitSet();

for i = 0 to 10 million

HashMap.get (i)

if number exist
arp.set(i , true)

else
arp.set(i , false)

After that from bitset I get if number i exist or not. However, I found this bitset operation is quite slow (tried with string = string + 0/1 also, more slower). Can anybody help me how to replace this operation with a faster one.

Answer 1

Your code is really difficult to read clearly, but I suspect you’re just trying to set bits in the BitSet that are keys from your HashMap?

In that case, your code should just be more or less

BitSet bits = new BitSet(10000000);
for (Integer k : map.keySet()) {
  bits.set(k);
}

Even if this wasn’t what you meant, as a general rule, BitSet is blazing fast; I suspect it’s the rest of your code that’s slow.