9.4. Comparing java.util.concurrent.ConcurrentMap and javax.cache.Cache APIs

Here is a brief comparison of the data manipulation APIs provided by java.util.concurrent.ConcurrentMap and javax.cache.Cache APIs:

Table 9.1. java.util.concurrent.ConcurrentMap and javax.cache.Cache Comparison

Operation
java.util.concurrent.ConcurrentMap<K,V>
javax.cache.Cache<K,V>
store and no return N/A
void put(K key)
store and return previous value
V put(K key)
V getAndPut(K key)
store if not present
V putIfAbsent(K key, V Value)
boolean putIfAbsent(K key, V value)
retrieve
V get(Object key)
V get(K key)
delete if present
V remove(Object key)
boolean remove(K key)
delete and return previous value
V remove(Object key)
V getAndRemove(K key)
delete conditional
boolean remove(Object key, Object value)
boolean remove(K key, V oldValue)
replace if present
V replace(K key, V value)
boolean replace(K key, V value)
replace and return previous value
V replace(K key, V value)
V getAndReplace(K key, V value)
replace conditional
boolean replace(K key, V oldValue, V newValue)
boolean replace(K key, V oldValue, V newValue)
Comparing the two APIs it can be seen that, where possible, JCache avoids returning the previous value to avoid operations doing expensive network or IO operations. This is an overriding principle in the design of the JCache API. In fact, there is a set of operations that are present in java.util.concurrent.ConcurrentMap, but are not present in the javax.cache.Cache because they could be expensive to compute in a distributed cache. The only exception is iterating over the contents of the cache:

Table 9.2. javax.cache.Cache avoiding returns

Operation
java.util.concurrent.ConcurrentMap<K,V>
javax.cache.Cache<K,V>
calculate size of cache
int size()
N/A
return all keys in the cache
Set<K> keySet()
N/A
return all values in the cache
Collection<V> values()
N/A
return all entries in the cache
Set<Map.Entry<K, V>> entrySet()
N/A
iterate over the cache use iterator() method on keySet, values, or entrySet
Iterator<Cache.Entry<K, V>> iterator()