it.units.malelab.ege.util.distance.CachedDistance.java Source code

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Here is the source code for it.units.malelab.ege.util.distance.CachedDistance.java

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package it.units.malelab.ege.util.distance;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.util.Arrays;
import java.util.List;

/**
 *
 * @author eric
 */
public class CachedDistance<T> implements Distance<T> {

    private transient LoadingCache<List<T>, Double> cache;
    private final Distance<T> distance;

    private static final int CACHE_SIZE = 10000;

    public CachedDistance(Distance<T> distance) {
        this.distance = distance;
        buildCache();
    }

    @Override
    public double d(T t1, T t2) {
        return cache.getUnchecked(Arrays.asList(t1, t2));
    }

    private void buildCache() {
        cache = CacheBuilder.newBuilder().maximumSize(CACHE_SIZE).build(new CacheLoader<List<T>, Double>() {
            @Override
            public Double load(List<T> ts) throws Exception {
                double d = distance.d(ts.get(0), ts.get(1));
                cache.put(Arrays.asList(ts.get(1), ts.get(0)), d); //put pair in the other order
                return d;
            }
        });
    }

    private void readObject(ObjectInputStream inputStream) throws IOException, ClassNotFoundException {
        inputStream.defaultReadObject();
        buildCache();
    }

}