concurrency-use-2.java

import java.math.BigInteger

/**
 * Clients can use this class instead, which means they only need fill in the 
 * V compute(K) method
 */ 
abstract class ConcCache2<K, V> {
  
  private final ConcCache<K, V> cache = new ConcCache<>();
  
  /** The computation */
  protected abstract V compute(K k);
  
  public final V get(final K k) {
    return cache.get(new Computation<K, V>(){
      public K key() { return k; }
      public V compute() { return compute(key()); }
    })
  }
}

/**
 * Client cache implementation is now a bit simpler; they only need fill in a single method
 */ 
class ProbablePrimeCache {
  private final int ACCURACY = 8;
  
  private static ConcCache2<BigInteger, Boolean> cache = new ConcCache2<BigInteger, Boolean>() {
    protected Boolean compute(BigInteger i) { return i.isProbablePrime(ACCURACY); }
  };
  
  public static isProbablePrime(BigInteger i) { return cache.get(i); }
}