Package com.ctc.wstx.util
Class WordSet
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- com.ctc.wstx.util.WordSet
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public final class WordSet extends java.lang.Object
An efficient (both memory and time) implementation of a Set used to verify that a given word is contained within the set. The general usage pattern is expected to be such that most checks are positive, ie. that the word indeed is contained in the set.Performance of the set is comparable to that of
TreeSet
for Strings, ie. 2-3x slower thanHashSet
when using pre-constructed Strings. This is generally result of algorithmic complexity of structures; Word and Tree sets are roughly logarithmic to the whole data, whereas Hash set is linear to the length of key. However:- WordSet can use char arrays as keys, without constructing Strings. In cases where there is no (need for) Strings, WordSet seems to be about twice as fast, even without considering additional GC caused by temporary String instances.
- WordSet is more compact in its memory presentation; if Strings are shared its size is comparable to optimally filled HashSet, and if no such Strings exists, its much more compact (relatively speaking)
Although this is an efficient set for specific set of usage patterns, one restriction is that the full set of words to include has to be known before constructing the set. Also, the size of the set is limited to total word content of about 20k characters; factory method does verify the limit and indicates if an instance can not be created.
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Nested Class Summary
Nested Classes Modifier and Type Class Description private static class
WordSet.Builder
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Field Summary
Fields Modifier and Type Field Description (package private) static char
CHAR_NULL
(package private) char[]
mData
Compressed presentation of the word set.(package private) static int
MIN_BINARY_SEARCH
This is actually just a guess; but in general linear search should be faster for short sequences (definitely for 4 or less; maybe up to 8 or less?)(package private) static int
NEGATIVE_OFFSET
Offset added to numbers to mark 'negative' numbers.
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Constructor Summary
Constructors Modifier Constructor Description private
WordSet(char[] data)
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description static char[]
constructRaw(java.util.TreeSet<java.lang.String> wordSet)
static WordSet
constructSet(java.util.TreeSet<java.lang.String> wordSet)
static boolean
contains(char[] data, char[] str, int start, int end)
boolean
contains(char[] buf, int start, int end)
static boolean
contains(char[] data, java.lang.String str)
boolean
contains(java.lang.String str)
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Field Detail
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CHAR_NULL
static final char CHAR_NULL
- See Also:
- Constant Field Values
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NEGATIVE_OFFSET
static final int NEGATIVE_OFFSET
Offset added to numbers to mark 'negative' numbers. Asymmetric, since range of negative markers needed is smaller than positive numbers...- See Also:
- Constant Field Values
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MIN_BINARY_SEARCH
static final int MIN_BINARY_SEARCH
This is actually just a guess; but in general linear search should be faster for short sequences (definitely for 4 or less; maybe up to 8 or less?)- See Also:
- Constant Field Values
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mData
final char[] mData
Compressed presentation of the word set.
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Method Detail
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constructSet
public static WordSet constructSet(java.util.TreeSet<java.lang.String> wordSet)
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constructRaw
public static char[] constructRaw(java.util.TreeSet<java.lang.String> wordSet)
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contains
public boolean contains(char[] buf, int start, int end)
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contains
public static boolean contains(char[] data, char[] str, int start, int end)
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contains
public boolean contains(java.lang.String str)
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contains
public static boolean contains(char[] data, java.lang.String str)
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