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Why did guava/java use possible.isPresent() as opposed to Optional.isPresent(possible)?

The idea of Optional is not to prevent all NPEs. The idea is to make it clear that an API method can return an absent value, and to force the caller to be aware of that and deal with it.

Of course, if this method returns null instead of an Optional, you'll still get a NPE, but that's a giant design issue. A method returning an Optional should return an Optional (present or absent), not null.

And it's much more natural, in a OO language, to access the state of an object using methods of this object rather than a static method.

Categories : Java

Related to : Why did guava/java use possible.isPresent() as opposed to Optional.isPresent(possible)?
is there a way in excel (as opposed to vba) to use index match to return a value with a max function in the matching criteria?
Try =INDEX(C2:C10,MATCH(MAX(IF(A2:A10=E1,B2:B10,0)),B2:B10,0)) This is an array formula and must be confirmed with CTRL-SHIFT-Enter

Categories : Excel
Big-O of containsValue for Guava HashBiMap
A PROPERLY IMPLEMENTED two-way HashMap (In this case, a HashBiMap) indeed has a runtime complexity of O(1) for containsKey and containsValue.

Categories : Java
Automatic cache refresh with Guava
A LoadingCache built with LoadingCache<K, V> cache = CacheBuilder.newBuilder() .refreshAfterWrite(15, TimeUnit.MINUTES) .maximumSize(100) .build(new MyCacheLoader()); will not refresh automatically by itself an entry every 15 minutes, as the cache does not create threads to do any kind of management (expiring or refreshing entries). If you call cache.get(someKey) t

Categories : Java
Guava cache for custom POJO
Use generics: class UserCacheLoader extends CacheLoader<Long, User> { @Override public User load(Long key) throws Exception { // ??? } } store(User) can be implemented with Cache.put, just like you'd expect. getKeys() can be implemented with cache.asMap().keySet().

Categories : Java
Compatable Guava version for JAVA 7
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Categories : Java
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