Class InternCache

java.lang.Object

java.util.AbstractMap<String,String>

java.util.concurrent.ConcurrentHashMap<String,String>

tools.jackson.core.util.InternCache

All Implemented Interfaces:

Serializable, ConcurrentMap<String,String>, Map<String,String>

public final class InternCache
extends ConcurrentHashMap<String,String>

Singleton class that adds a simple first-level cache in front of regular String.intern() functionality. This is done as a minor performance optimization, to avoid calling native intern() method in cases where same String is being interned multiple times. Note: that this class extends ConcurrentHashMap is an implementation detail -- no code should ever directly call ConcurrentHashMap methods.

See Also:

• Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class ConcurrentHashMap

ConcurrentHashMap.KeySetView<K,V>

Nested classes/interfaces inherited from class AbstractMap

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

Nested classes/interfaces inherited from interface Map

Map.Entry<K,V>

Field Summary

Fields

Modifier and Type	Field	Description
private static final int	DEFAULT_MAX_ENTRIES	Size to use is somewhat arbitrary, so let's choose something that's neither too small (low hit ratio) nor too large (waste of memory).
static final InternCache	instance
private final ReentrantLock	lock	As minor optimization let's try to avoid "flush storms", cases where multiple threads might try to concurrently flush the map.
private static final long	serialVersionUID

Constructor Summary

Constructors

Constructor	Description
InternCache()
InternCache(int maxSize, float loadFactor, int concurrency)

Method Summary

Modifier and Type	Method	Description
String	intern(String input)

Methods inherited from class ConcurrentHashMap

clear, compute, computeIfAbsent, computeIfPresent, contains, containsKey, containsValue, elements, entrySet, equals, forEach, forEach, forEach, forEachEntry, forEachEntry, forEachKey, forEachKey, forEachValue, forEachValue, get, getOrDefault, hashCode, isEmpty, keys, keySet, keySet, mappingCount, merge, newKeySet, newKeySet, put, putAll, putIfAbsent, reduce, reduceEntries, reduceEntries, reduceEntriesToDouble, reduceEntriesToInt, reduceEntriesToLong, reduceKeys, reduceKeys, reduceKeysToDouble, reduceKeysToInt, reduceKeysToLong, reduceToDouble, reduceToInt, reduceToLong, reduceValues, reduceValues, reduceValuesToDouble, reduceValuesToInt, reduceValuesToLong, remove, remove, replace, replace, replaceAll, search, searchEntries, searchKeys, searchValues, size, toString, values

Methods inherited from class AbstractMap

clone

Methods inherited from class Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Details

serialVersionUID

private static final long serialVersionUID

See Also:

• Constant Field Values

DEFAULT_MAX_ENTRIES

private static final int DEFAULT_MAX_ENTRIES

Size to use is somewhat arbitrary, so let's choose something that's neither too small (low hit ratio) nor too large (waste of memory).

One consideration is possible attack via colliding String.hashCode(); because of this, limit to reasonably low setting.

Increased to 200 (from 100) in 2.18

See Also:

• Constant Field Values

instance

public static final InternCache instance

lock

private final ReentrantLock lock

As minor optimization let's try to avoid "flush storms", cases where multiple threads might try to concurrently flush the map.

Constructor Details

InternCache

public InternCache()

InternCache

public InternCache(int maxSize,
 float loadFactor,
 int concurrency)

Method Details

intern

public String intern(String input)