# Package gnu.trove

GNU Trove: High performance collections for Java.

See: Description

Interface Summary
Interface | Description
--- | ---
TByteByteProcedure | Interface for procedures that take two parameters of type byte and byte.
TByteDoubleProcedure | Interface for procedures that take two parameters of type byte and double.
TByteFloatProcedure | Interface for procedures that take two parameters of type byte and float.
TByteFunction | Interface for functions that accept and return one byte primitive.
TByteHashingStrategy | Interface to support pluggable hashing strategies in maps and sets.
TByteIntProcedure | Interface for procedures that take two parameters of type byte and int.
TByteLongProcedure | Interface for procedures that take two parameters of type byte and long.
TByteObjectProcedure<T> | Interface for procedures that take two parameters of type byte and Object.
TByteProcedure | Interface for procedures with one byte parameter.
TByteShortProcedure | Interface for procedures that take two parameters of type byte and short.
TDoubleByteProcedure | Interface for procedures that take two parameters of type double and byte.
TDoubleDoubleProcedure | Interface for procedures that take two parameters of type double and double.
TDoubleFloatProcedure | Interface for procedures that take two parameters of type double and float.
TDoubleFunction | Interface for functions that accept and return one double primitive.
TDoubleHashingStrategy | Interface to support pluggable hashing strategies in maps and sets.
TDoubleIntProcedure | Interface for procedures that take two parameters of type double and int.
TDoubleLongProcedure | Interface for procedures that take two parameters of type double and long.
TDoubleObjectProcedure<T> | Interface for procedures that take two parameters of type double and Object.
TDoubleProcedure | Interface for procedures with one double parameter.
TDoubleShortProcedure | Interface for procedures that take two parameters of type double and short.
TFloatByteProcedure | Interface for procedures that take two parameters of type float and byte.
TFloatDoubleProcedure | Interface for procedures that take two parameters of type float and double.
TFloatFloatProcedure | Interface for procedures that take two parameters of type float and float.
TFloatFunction | Interface for functions that accept and return one float primitive.
TFloatHashingStrategy | Interface to support pluggable hashing strategies in maps and sets.
TFloatIntProcedure | Interface for procedures that take two parameters of type float and int.
TFloatLongProcedure | Interface for procedures that take two parameters of type float and long.
TFloatObjectProcedure<T> | Interface for procedures that take two parameters of type float and Object.
TFloatProcedure | Interface for procedures with one float parameter.
TFloatShortProcedure | Interface for procedures that take two parameters of type float and short.
TIntByteProcedure | Interface for procedures that take two parameters of type int and byte.
TIntDoubleProcedure | Interface for procedures that take two parameters of type int and double.
TIntFloatProcedure | Interface for procedures that take two parameters of type int and float.
TIntFunction | Interface for functions that accept and return one int primitive.
TIntHashingStrategy | Interface to support pluggable hashing strategies in maps and sets.
TIntIntProcedure | Interface for procedures that take two parameters of type int and int.
TIntLongProcedure | Interface for procedures that take two parameters of type int and long.
TIntObjectProcedure<T> | Interface for procedures that take two parameters of type int and Object.
TIntProcedure | Interface for procedures with one int parameter.
TIntShortProcedure | Interface for procedures that take two parameters of type int and short.
TLinkable | Interface for Objects which can be inserted into a TLinkedList.
TLongByteProcedure | Interface for procedures that take two parameters of type long and byte.
TLongDoubleProcedure | Interface for procedures that take two parameters of type long and double.
TLongFloatProcedure | Interface for procedures that take two parameters of type long and float.
TLongFunction | Interface for functions that accept and return one long primitive.
TLongHashingStrategy | Interface to support pluggable hashing strategies in maps and sets.
TLongIntProcedure | Interface for procedures that take two parameters of type long and int.
TLongLongProcedure | Interface for procedures that take two parameters of type long and long.
TLongObjectProcedure<T> | Interface for procedures that take two parameters of type long and Object.
TLongProcedure | Interface for procedures with one long parameter.
TLongShortProcedure | Interface for procedures that take two parameters of type long and short.
TObjectByteProcedure<K> | Interface for procedures that take two parameters of type Object and byte.
TObjectDoubleProcedure<K> | Interface for procedures that take two parameters of type Object and double.
TObjectFloatProcedure<K> | Interface for procedures that take two parameters of type Object and float.
TObjectFunction<T,R> | Interface for functions that accept and return one Object reference.
TObjectHashingStrategy<T> | Interface to support pluggable hashing strategies in maps and sets.
TObjectIntProcedure<K> | Interface for procedures that take two parameters of type Object and int.
TObjectLongProcedure<K> | Interface for procedures that take two parameters of type Object and long.
TObjectObjectProcedure<K,V> | Interface for procedures that take two Object parameters.
TObjectProcedure<T> | Interface for procedures with one Object parameter.
TObjectShortProcedure<K> | Interface for procedures that take two parameters of type Object and short.
TShortByteProcedure | Interface for procedures that take two parameters of type short and byte.
TShortDoubleProcedure | Interface for procedures that take two parameters of type short and double.
TShortFloatProcedure | Interface for procedures that take two parameters of type short and float.
TShortFunction | Interface for functions that accept and return one short primitive.
TShortHashingStrategy | Interface to support pluggable hashing strategies in maps and sets.
TShortIntProcedure | Interface for procedures that take two parameters of type short and int.
TShortLongProcedure | Interface for procedures that take two parameters of type short and long.
TShortObjectProcedure<T> | Interface for procedures that take two parameters of type short and Object.
TShortProcedure | Interface for procedures with one short parameter.
TShortShortProcedure | Interface for procedures that take two parameters of type short and short.

Class Summary
Class | Description
--- | ---
Decorators | This is a static utility class that provides functions for simplifying creation of decorators.
HashFunctions | Provides various hash functions.
PrimeFinder | Used to keep hash table capacities prime numbers.
TByteArrayList | A resizable, array-backed list of byte primitives.
TByteByteHashMap | An open addressed Map implementation for byte keys and byte values.
TByteByteIterator | Iterator for maps of type byte and byte.
TByteDoubleHashMap | An open addressed Map implementation for byte keys and double values.
TByteDoubleIterator | Iterator for maps of type byte and double.
TByteFloatHashMap | An open addressed Map implementation for byte keys and float values.
TByteFloatIterator | Iterator for maps of type byte and float.
TByteHash | An open addressed hashing implementation for byte primitives.
TByteHashSet | An open addressed set implementation for byte primitives.
TByteIntHashMap | An open addressed Map implementation for byte keys and int values.
TByteIntIterator | Iterator for maps of type byte and int.
TByteIterator | Iterator for byte collections.
TByteLongHashMap | An open addressed Map implementation for byte keys and long values.
TByteLongIterator | Iterator for maps of type byte and long.
TByteObjectHashMap<V> | An open addressed Map implementation for byte keys and Object values.
TByteObjectIterator<V> | Iterator for maps of type byte and Object.
TByteShortHashMap | An open addressed Map implementation for byte keys and short values.
TByteShortIterator | Iterator for maps of type byte and short.
TByteStack | A stack of byte primitives, backed by a TByteArrayList.
TDoubleArrayList | A resizable, array-backed list of double primitives.
TDoubleByteHashMap | An open addressed Map implementation for double keys and byte values.
TDoubleByteIterator | Iterator for maps of type double and byte.
TDoubleDoubleHashMap | An open addressed Map implementation for double keys and double values.
TDoubleDoubleIterator | Iterator for maps of type double and double.
TDoubleFloatHashMap | An open addressed Map implementation for double keys and float values.
TDoubleFloatIterator | Iterator for maps of type double and float.
TDoubleHash | An open addressed hashing implementation for double primitives.
TDoubleHashSet | An open addressed set implementation for double primitives.
TDoubleIntHashMap | An open addressed Map implementation for double keys and int values.
TDoubleIntIterator | Iterator for maps of type double and int.
TDoubleIterator | Iterator for double collections.
TDoubleLongHashMap | An open addressed Map implementation for double keys and long values.
TDoubleLongIterator | Iterator for maps of type double and long.
TDoubleObjectHashMap<V> | An open addressed Map implementation for double keys and Object values.
TDoubleObjectIterator<V> | Iterator for maps of type double and Object.
TDoubleShortHashMap | An open addressed Map implementation for double keys and short values.
TDoubleShortIterator | Iterator for maps of type double and short.
TDoubleStack | A stack of double primitives, backed by a TDoubleArrayList.
TFloatArrayList | A resizable, array-backed list of float primitives.
TFloatByteHashMap | An open addressed Map implementation for float keys and byte values.
TFloatByteIterator | Iterator for maps of type float and byte.
TFloatDoubleHashMap | An open addressed Map implementation for float keys and double values.
TFloatDoubleIterator | Iterator for maps of type float and double.
TFloatFloatHashMap | An open addressed Map implementation for float keys and float values.
TFloatFloatIterator | Iterator for maps of type float and float.
TFloatHash | An open addressed hashing implementation for float primitives.
TFloatHashSet | An open addressed set implementation for float primitives.
TFloatIntHashMap | An open addressed Map implementation for float keys and int values.
TFloatIntIterator | Iterator for maps of type float and int.
TFloatIterator | Iterator for float collections.
TFloatLongHashMap | An open addressed Map implementation for float keys and long values.
TFloatLongIterator | Iterator for maps of type float and long.
TFloatObjectHashMap<V> | An open addressed Map implementation for float keys and Object values.
TFloatObjectIterator<V> | Iterator for maps of type float and Object.
TFloatShortHashMap | An open addressed Map implementation for float keys and short values.
TFloatShortIterator | Iterator for maps of type float and short.
TFloatStack | A stack of float primitives, backed by a TFloatArrayList.
THash | Base class for hashtables that use open addressing to resolve collisions.
THashMap<K,V> | An implementation of the Map interface which uses an open addressed hash table to store its contents.
THashSet<E> | An implementation of the `Set` interface that uses an open-addressed hash table to store its contents.
TIntArrayList | A resizable, array-backed list of int primitives.
TIntByteHashMap | An open addressed Map implementation for int keys and byte values.
TIntByteIterator | Iterator for maps of type int and byte.
TIntDoubleHashMap | An open addressed Map implementation for int keys and double values.
TIntDoubleIterator | Iterator for maps of type int and double.
TIntFloatHashMap | An open addressed Map implementation for int keys and float values.
TIntFloatIterator | Iterator for maps of type int and float.
TIntHash | An open addressed hashing implementation for int primitives.
TIntHashSet | An open addressed set implementation for int primitives.
TIntIntHashMap | An open addressed Map implementation for int keys and int values.
TIntIntIterator | Iterator for maps of type int and int.
TIntIterator | Iterator for int collections.
TIntLongHashMap | An open addressed Map implementation for int keys and long values.
TIntLongIterator | Iterator for maps of type int and long.
TIntObjectHashMap<V> | An open addressed Map implementation for int keys and Object values.
TIntObjectIterator<V> | Iterator for maps of type int and Object.
TIntShortHashMap | An open addressed Map implementation for int keys and short values.
TIntShortIterator | Iterator for maps of type int and short.
TIntStack | A stack of int primitives, backed by a TIntArrayList.
TLinkableAdapter | Adapter for TLinkable interface which implements the interface and can therefore be extended trivially to create TLinkable objects without having to implement the obvious.
TLinkedList<T extends TLinkable> | A LinkedList implementation which holds instances of type `TLinkable`.
TLongArrayList | A resizable, array-backed list of long primitives.
TLongByteHashMap | An open addressed Map implementation for long keys and byte values.
TLongByteIterator | Iterator for maps of type long and byte.
TLongDoubleHashMap | An open addressed Map implementation for long keys and double values.
TLongDoubleIterator | Iterator for maps of type long and double.
TLongFloatHashMap | An open addressed Map implementation for long keys and float values.
TLongFloatIterator | Iterator for maps of type long and float.
TLongHash | An open addressed hashing implementation for long primitives.
TLongHashSet | An open addressed set implementation for long primitives.
TLongIntHashMap | An open addressed Map implementation for long keys and int values.
TLongIntIterator | Iterator for maps of type long and int.
TLongIterator | Iterator for long collections.
TLongLongHashMap | An open addressed Map implementation for long keys and long values.
TLongLongIterator | Iterator for maps of type long and long.
TLongObjectHashMap<V> | An open addressed Map implementation for long keys and Object values.
TLongObjectIterator<V> | Iterator for maps of type long and Object.
TLongShortHashMap | An open addressed Map implementation for long keys and short values.
TLongShortIterator | Iterator for maps of type long and short.
TLongStack | A stack of long primitives, backed by a TLongArrayList.
TObjectByteHashMap<K> | An open addressed Map implementation for Object keys and byte values.
TObjectByteIterator<K> | Iterator for maps of type Object and byte.
TObjectDoubleHashMap<K> | An open addressed Map implementation for Object keys and double values.
TObjectDoubleIterator<K> | Iterator for maps of type Object and double.
TObjectFloatHashMap<K> | An open addressed Map implementation for Object keys and float values.
TObjectFloatIterator<K> | Iterator for maps of type Object and float.
TObjectHash<T> | An open addressed hashing implementation for Object types.
TObjectIdentityHashingStrategy<T> | This object hashing strategy uses the System.identityHashCode method to provide identity hash codes.
TObjectIntHashMap<K> | An open addressed Map implementation for Object keys and int values.
TObjectIntIterator<K> | Iterator for maps of type Object and int.
TObjectLongHashMap<K> | An open addressed Map implementation for Object keys and long values.
TObjectLongIterator<K> | Iterator for maps of type Object and long.
TObjectShortHashMap<K> | An open addressed Map implementation for Object keys and short values.
TObjectShortIterator<K> | Iterator for maps of type Object and short.
TPrimitiveHash | The base class for hashtables of primitive values.
TShortArrayList | A resizable, array-backed list of short primitives.
TShortByteHashMap | An open addressed Map implementation for short keys and byte values.
TShortByteIterator | Iterator for maps of type short and byte.
TShortDoubleHashMap | An open addressed Map implementation for short keys and double values.
TShortDoubleIterator | Iterator for maps of type short and double.
TShortFloatHashMap | An open addressed Map implementation for short keys and float values.
TShortFloatIterator | Iterator for maps of type short and float.
TShortHash | An open addressed hashing implementation for short primitives.
TShortHashSet | An open addressed set implementation for short primitives.
TShortIntHashMap | An open addressed Map implementation for short keys and int values.
TShortIntIterator | Iterator for maps of type short and int.
TShortIterator | Iterator for short collections.
TShortLongHashMap | An open addressed Map implementation for short keys and long values.
TShortLongIterator | Iterator for maps of type short and long.
TShortObjectHashMap<V> | An open addressed Map implementation for short keys and Object values.
TShortObjectIterator<V> | Iterator for maps of type short and Object.
TShortShortHashMap | An open addressed Map implementation for short keys and short values.
TShortShortIterator | Iterator for maps of type short and short.
TShortStack | A stack of short primitives, backed by a TShortArrayList.

## Package gnu.trove Description

GNU Trove: High performance collections for Java.

## Objectives

The GNU Trove library has two objectives:

1. Provide "free" (as in "free speech" and "free beer"), fast, lightweight implementations of the `java.util` Collections API. These implementations are designed to be pluggable replacements for their JDK equivalents.
2. Whenever possible, provide the same collections support for primitive types. This gap in the JDK is often addressed by using the "wrapper" classes (`java.lang.Integer`, `java.lang.Float`, etc.) with Object-based collections. For most applications, however, collections which store primitives directly will require less space and yield significant performance gains.

## Hashtable techniques

The Trove maps/sets use open addressing instead of the chaining approach taken by the JDK hashtables. This eliminates the need to create Map.Entry wrappper objects for every item in a table and so reduces the `O` (big-oh) in the performance of the hashtable algorithm. The size of the tables used in Trove's maps/sets is always a prime number, improving the probability of an optimal distribution of entries across the table, and so reducing the the likelihood of performance-degrading collisions. Trove sets are not backed by maps, and so using a THashSet does not result in the allocation of an unused "values" array.

## Hashing strategies

Trove's maps/sets support the use of custom `hashing strategies`, allowing you to tune collections based on characteristics of the input data. This feature also allows you to define hash functions when it is not feasible to override Object.hashCode(). For example, the java.lang.String class is final, and its implementation of hashCode() takes `O(n)` time to complete. In some applications, however, it may be possible for a custom hashing function to save time by skipping portions of the string that are invariant.

Using java.util.HashMap, it is not possible to use Java language arrays as keys. For example, this code:

        char[] foo, bar;
        foo = new char[] {'a','b','c'};
        bar = new char[] {'a','b','c'};
        System.out.println(foo.hashCode() == bar.hashCode() ? "equal" : "not equal");
        System.out.println(foo.equals(bar) ? "equal" : "not equal");

produces this output:

        not equal
        not equal

And so an entry stored in a java.util.HashMap with foo as a key could not be retrieved with bar, since there is no way to override hashCode() or equals() on language array objects.

In a gnu.trove.THashMap, however, you can implement a TObjectHashingStrategy to enable hashing on arrays:

        class CharArrayStrategy implements TObjectHashingStrategy {
            public int computeHashCode(Object o) {
                char[] c = (char[])o;
                // use the shift-add-xor class of string hashing functions
                // cf. Ramakrishna and Zobel, "Performance in Practice of String Hashing Functions"
                int h = 31; // seed chosen at random
                for (int i = 0; i < c.length; i++) { // could skip invariants
                    h = h ^ ((h << 5) + (h >> 2) + c[i]); // L=5, R=2 works well for ASCII input
                }
                return h;
            }

            public boolean equals(Object o1, Object o2) {
                char[] c1 = (char[])o1;
                char[] c2 = (char[])o2;
                if (c1.length != c2.length) { // could drop this check for fixed-length keys
                    return false;
                }
                for (int i = 0, len = c1.length; i < len; i++) { // could skip invariants
                    if (c1[i] != c2[i]) {
                        return false;
                    }
                }
                return true;
            }
        }

## Iterators in primitive collections

As of release 0.1.7, Trove's primitive mappings include access through Iterators as well as procedures and functions. The API documentation on those classes contains several examples showing how these can be used effectively and explaining why their semantics differ from those of `java.util.Iterator.`

## Miscellaneous

N.B. using `Map.entrySet` on a Trove Map is supported, but not encouraged. The reason is that this API requires the creation of the Map.Entry Objects that all other parts of Trove manage to avoid. An alternative is to implement the appropriate `Procedure` interface and use it to invoke the Map's `forEachEntry` API. `Map.keySet` and `Map.values` are not similarly encumbered; nevertheless, the `forEachKey`, `forEachValue`, and `transformValues` APIs will yield slightly better performance at the cost of compatibility with the interface of `java.util.Map`.

Last modified: Mon Sep 23 18:22:39 PDT 2002