edu.washington.cs.cupid.standard.MostFrequent.java Source code

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/*******************************************************************************
 * Copyright (c) 2013 Todd Schiller.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     Todd Schiller - initial API, implementation, and documentation
 ******************************************************************************/
package edu.washington.cs.cupid.standard;

import java.util.List;

import org.eclipse.core.runtime.IProgressMonitor;

import com.google.common.collect.HashMultiset;
import com.google.common.collect.Multiset;
import com.google.common.collect.Multisets;
import com.google.common.reflect.TypeToken;

import edu.washington.cs.cupid.capability.linear.GenericLinearCapability;
import edu.washington.cs.cupid.capability.linear.LinearJob;
import edu.washington.cs.cupid.capability.linear.LinearStatus;

/**
 * A capability that computes the most frequent element in a collection.
 * @author Todd Schiller
 * @param <V> the collection element type
 */
public final class MostFrequent<V> extends GenericLinearCapability<List<V>, V> {

    // TODO make efficient

    /**
     * A capability that computes the most frequent element in a collection.
     */
    public MostFrequent() {
        super("Most Frequent Element", "Get the most frequent element in a collection", Flag.PURE);
    }

    @Override
    public LinearJob<List<V>, V> getJob(final List<V> input) {
        return new LinearJob<List<V>, V>(this, input) {
            @Override
            protected LinearStatus<V> run(final IProgressMonitor monitor) {
                try {
                    monitor.beginTask(getName(), 100);

                    Multiset<V> set = HashMultiset.create();
                    set.addAll(input);
                    for (V val : Multisets.copyHighestCountFirst(set)) {
                        return LinearStatus.makeOk(getCapability(), val);
                    }

                    return LinearStatus.<V>makeError(
                            new IllegalArgumentException("Cannot get most frequent element of empty collection"));
                } catch (Exception ex) {
                    return LinearStatus.<V>makeError(ex);
                } finally {
                    monitor.done();
                }
            }
        };
    }

    @Override
    public TypeToken<List<V>> getInputType() {
        return new TypeToken<List<V>>(getClass()) {
        };
    }

    @Override
    public TypeToken<V> getOutputType() {
        return new TypeToken<V>(getClass()) {
        };
    }

}