Java in a Nutshell, 5th Edition

Name

BitSet

Synopsis

This class implements an array or list of boolean values storing them using a very compact representation that requires only about one bit per value stored. It implements methods for setting, querying, and flipping the values stored at any given position within the list, for counting the number of true values stored in the list, and for finding the next true or false value in the list. It also defines a number of methods that perform bitwise boolean operations on two BitSet objects. Despite its name, BitSet does not implement the Set interface, and does not even have the behavior associated with a set; it is a list or vector for boolean values, but is not related to the List interface or Vector class. This class was introduced in Java 1.0, but was substantially enhanced in Java 1.4; note that many of the methods described below are only available in Java 1.4 and later.

Create a BitSet with the BitSet( ) constructor. You may optionally specify a size (the number of bits) for the BitSet, but this merely provides an optimization since a BitSet will grow as needed to accomodate any number of boolean values. BitSet does not define a precise notion of the size of a “set.” The size( ) method returns the number of boolean values that can be stored before more internal storage needs to be allocated. The length( ) method returns one more than the highest index of a set bit (i.e., a true value). This means that a BitSet that contains all false values will have a length( ...