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package com.ctc.wstx.util;
import java.util.LinkedHashMap;
import java.util.Map;
/**
* Singleton class that implements "fast intern" functionality, essentially
* adding a layer that caches Strings that have been previously intern()ed,
* but that probably shouldn't be added to symbol tables.
* This is usually used by improving intern()ing of things like namespace
* URIs.
*
* Note: that this class extends {@link LinkedHashMap} is an implementation
* detail -- no code should ever directly call Map methods.
*/
public final class InternCache extends LinkedHashMap //
{
private static final long serialVersionUID = 1L;
/**
* Let's create cache big enough to usually have enough space for
* all entries... (assuming NS URIs only)
*/
private final static int DEFAULT_SIZE = 64;
/**
* Let's limit to hash area size of 1024.
*/
private final static int MAX_SIZE = 660;
private final static InternCache sInstance = new InternCache();
private InternCache() {
/* Let's also try to seriously minimize collisions... since
* collisions are likely to be more costly here, with longer
* Strings; so let's use 2/3 ratio (67%) instead of default
* (75%)
*/
super(DEFAULT_SIZE, 0.6666f, false);
}
public static InternCache getInstance() {
return sInstance;
}
public String intern(String input)
{
String result;
/* Let's split sync block to help in edge cases like
* [WSTX-220]
*/
synchronized (this) {
result = (String) get(input);
}
if (result == null) {
result = input.intern();
synchronized (this) {
put(result, result);
}
}
return result;
}
// We will force maximum size here (for [WSTX-237])
//@Override protected boolean removeEldestEntry(Map.Entry eldest)
protected boolean removeEldestEntry(Map.Entry eldest)
{
return size() > MAX_SIZE;
}
}