org.apache.xml.dtm.ref
public class DTMStringPool extends Object
DTMStringPool is an "interning" mechanism for strings. It will create a stable 1:1 mapping between a set of string values and a set of integer index values, so the integers can be used to reliably and uniquely identify (and when necessary retrieve) the strings.
Design Priorities:
Implementation detail: A standard Hashtable is relatively inefficient when looking up primitive int values, especially when we're already maintaining an int-to-string vector. So I'm maintaining a simple hash chain within this class.
NOTE: There is nothing in the code that has a real dependency upon String. It would work with any object type that implements reliable .hashCode() and .equals() operations. The API enforces Strings because it's safer that way, but this could trivially be turned into a general ObjectPool if one was needed.
Status: Passed basic test in main().
Field Summary | |
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static int | NULL |
Constructor Summary | |
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DTMStringPool(int chainSize)
Create a DTMStringPool using the given chain size
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DTMStringPool() |
Method Summary | |
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String | indexToString(int i) |
static void | main(String[] args) Command-line unit test driver. |
void | removeAllElements() |
int | stringToIndex(String s) |
Parameters: chainSize The size of the hash chain vector
Returns: string whose value is uniquely identified by this integer index.
Throws: java.lang.ArrayIndexOutOfBoundsException if index doesn't map to a string.
Returns: integer index uniquely identifying the value of this string.