libfastutil-java - 8.5.15+dfsg-1 main

Fastutil extends the Java™ Collections Framework by providing
type-specific maps, sets, lists and queues with a small memory footprint
and fast access and insertion; provides also big (64-bit) arrays, sets
and lists, and fast, practical I/O classes for binary and text files.
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The classes implement their standard counterpart interface (e.g., Map
for maps) and can be plugged into existing code. Moreover, they provide
additional features (such as bidirectional iterators) that are not
available in the standard classes.
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Besides objects and primitive types, fastutil classes provide support
for references, that is, objects that are compared using the equality
operator rather than the equals() method.