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I'm looking for a good Java BitSet example to work with 0 and 1s. I tried looking at the Javadocs but I don't understand the usage of the class by just reading that. For instance, how would the and, or, and xor methods work on two different BitSet objects?
For example:
BitSet bits1 = new BitSet(); BitSet bits2 = new BitSet(); bits2.set(1000001); bits1.set(1111111); bits2.and(bits1); System.out.println(bits2); If I do this it returns bits2 as empty why is that?
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BitSet is a class defined in the java. util package. It creates an array of bits represented by boolean values.
The BitSet class creates a special type of array that holds bit values. The BitSet array can increase in size as needed. This makes it similar to a vector of bits.
A BitSet is a very efficient for a set of non-negative integers within a (not too large) range. Much more efficient than arrays and hash maps. An EnumSet is implemented the same way as a BitSet .
The difference between a boolean array and a BitSet is essentially the same as the difference between an array of object references and a List.
For the specific problem you mentioned: when you called bits2.set(1000001), you set the one millionth and first bit to true. Then when you intersected with bits1, which had the one million, 111 thousand, and 111st bit set, they had no bits in common.
I think what you meant to do was
bits2.set(0); // set the 0th bit bits2.set(6); // set the 6th bit Does this help clear things up?
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