A primitive cache implementation. The SimpleCache allows to cache
lazily computable values. Subsequent calls to the computation algorithm with equal
parameters have to yield equal results.
Attention: The algorithm may not depend on itself in a circular manner. E.g. the following will lead
to a stack overflow:
SimpleCache cache = new SimpleCache(new Function() {
public V apply(K k) {
// DON'T DO THIS
if (k == k1) {
return cache.get(k2).method();
} else if (k == k2) {
return cache.get(k1).method();
}
return null;
}
});
The cache uses weak references to the keys but the values are strongly referenced. This leads
to the conclusion, that the computed values should not refer to the keys because no cache entry
will be reclaimend automatically. In such cases, clients have to discard the values for a key explicitly.
Please note that
Function.apply(Object) may be invoked concurrently while the cache
itself is threadsafe.