org.osgl.util

Class LFUCache<K,V>

java.lang.Object

org.osgl.util.LFUCache<K,V>

Type Parameters:

K -

V -

public class LFUCache<K,V>
extends Object

A simple thread-safe LFU cache.

Disclaim: the source code is adapted from https://github.com/Tsien/LFUCache/

Constructor Summary

Constructors

Constructor and Description
LFUCache(int cap, double evictFactor) Create a new LFU cache.

Method Summary

Modifier and Type	Method and Description
Integer	decr(K key, Integer delta) Decrements the value stored at key by delta.
V	get(K key) Get the value of key.
Integer	incr(K key, Integer delta) Increments the value stored at key by delta.
Map<K,V>	mget(List<K> keys) Returns the values of all specified keys.
void	mset(Map<K,V> data) Sets the given keys to their respective values.
void	print() Only for testing purpose Print the content of the cache in the order of frequency
void	set(K key, V value) Set key to hold the value.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LFUCache

public LFUCache(int cap,
                double evictFactor)

Create a new LFU cache.

Parameters:

cap - the size of the cache

evictFactor - the percentage of elements for replacement

Method Detail

get

public V get(K key)

Get the value of key. If the key does not exist, return null.

Parameters:

key - the key to query

Returns:

the value of the key

set

public void set(K key,
                V value)

Set key to hold the value. If key already holds a value, it is overwritten.

Parameters:

key - the key of the node

value - the value of the node

mget

public Map<K,V> mget(List<K> keys)

Returns the values of all specified keys. For every key that does not exist, null is returned.

Parameters:

keys - a list of keys to query

Returns:

query results, a map of key/val extracted

mset

public void mset(Map<K,V> data)

Sets the given keys to their respective values. MSET replaces existing values with new values, just as regular SET.

Parameters:

data - a map contains the key/val pairs to be set.

incr

public Integer incr(K key,
                    Integer delta)

Increments the value stored at key by delta. If the key does not exist, it is set to 0 before performing the operation. Only works for integer value. This function will increase frequency by 1

Parameters:

key - the key needed to be increased

delta - increment

Returns:

the value after increment

decr

public Integer decr(K key,
                    Integer delta)

Decrements the value stored at key by delta. If the key does not exist, it is set to 0 before performing the operation. Only works for integer value. This function will increase frequency by 2

Parameters:

key - the key needed to be decreased

delta - decrement

Returns:

the value after decrement

print

public void print()

Only for testing purpose Print the content of the cache in the order of frequency