public final Class InternCache

Class Inheritance

extends ConcurrentHashMap<String, String>

java.lang.Object
java.util.AbstractMap
java.util.concurrent.ConcurrentHashMap
com.fasterxml.jackson.core.util.InternCache

Imports

java.util.concurrent.ConcurrentHashMap, java.util.concurrent.locks.ReentrantLock

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.

Field Summary

Modifier and Type	Field and 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).
public 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 Hides java.util.concurrent.ConcurrentHashMap.serialVersionUID.

Constructor Summary

Access	Constructor and Description
public	InternCache()
public	InternCache(int maxSize, float loadFactor, int concurrency)

Method Summary

Modifier and Type	Method and Description
public String	intern(String input)

Field Detail

DEFAULT_MAX_ENTRIES back to summary

DEFAULT_MAX_ENTRIES	back to summary
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

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

instance	back to summary
public static final InternCache instance

lock	back to summary
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.

serialVersionUID	back to summary
private static final long serialVersionUID Hides java.util.concurrent.ConcurrentHashMap.serialVersionUID.

Constructor Detail

InternCache	back to summary
public InternCache()

InternCache	back to summary
public InternCache(int maxSize, float loadFactor, int concurrency)

Method Detail

intern	back to summary
public String intern(String input)