How to Implement a Time-Based Expiring Map/Cache in Java?

Java Time-Based Map/Cache with Expiring Keys

This question seeks a Java implementation that automatically expires entries based on a configurable timeout. The preferred solution avoids weak references, external configuration files, and manual implementation.

Answer

The Guava library provides a solution with its MapMaker class:

ConcurrentMap<Key, Graph> graphs = new MapMaker()
   .concurrencyLevel(4)
   .softKeys()
   .weakValues()
   .maximumSize(10000)
   .expiration(10, TimeUnit.MINUTES)
   .makeComputingMap(
       new Function<Key, Graph>() {
         public Graph apply(Key key) {
           return createExpensiveGraph(key);
         }
       });

For Guava version 10.0 and above, use CacheBuilder:

LoadingCache<Key, Graph> graphs = CacheBuilder.newBuilder()
    .maximumSize(10000)
    .expireAfterWrite(10, TimeUnit.MINUTES)
    .build(
        new CacheLoader<Key, Graph>() {
          public Graph load(Key key) throws AnyException {
            return createExpensiveGraph(key);
          }
        });

This implementation provides automatic key expiration, ensuring that entries are removed after a specified period.

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