org.apache.mahout.cf.taste.hadoop.RecommendedItemsWritable.java Source code

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Here is the source code for org.apache.mahout.cf.taste.hadoop.RecommendedItemsWritable.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.mahout.cf.taste.hadoop;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.hadoop.io.Writable;
import org.apache.mahout.cf.taste.impl.recommender.GenericRecommendedItem;
import org.apache.mahout.cf.taste.recommender.RecommendedItem;
import org.apache.mahout.math.Varint;

/**
 * A {@link Writable} which encapsulates a list of {@link RecommendedItem}s. This is the mapper (and reducer)
 * output, and represents items recommended to a user. The first item is the one whose estimated preference is
 * highest.
 */
public final class RecommendedItemsWritable implements Writable {

    private List<RecommendedItem> recommended;

    public RecommendedItemsWritable() {
        // do nothing
    }

    public RecommendedItemsWritable(List<RecommendedItem> recommended) {
        this.recommended = recommended;
    }

    public List<RecommendedItem> getRecommendedItems() {
        return recommended;
    }

    public void set(List<RecommendedItem> recommended) {
        this.recommended = recommended;
    }

    @Override
    public void write(DataOutput out) throws IOException {
        out.writeInt(recommended.size());
        for (RecommendedItem item : recommended) {
            Varint.writeSignedVarLong(item.getItemID(), out);
            out.writeFloat(item.getValue());
        }
    }

    @Override
    public void readFields(DataInput in) throws IOException {
        int size = in.readInt();
        recommended = new ArrayList<>(size);
        for (int i = 0; i < size; i++) {
            long itemID = Varint.readSignedVarLong(in);
            float value = in.readFloat();
            RecommendedItem recommendedItem = new GenericRecommendedItem(itemID, value);
            recommended.add(recommendedItem);
        }
    }

    @Override
    public String toString() {
        StringBuilder result = new StringBuilder(200);
        result.append('[');
        boolean first = true;
        for (RecommendedItem item : recommended) {
            if (first) {
                first = false;
            } else {
                result.append(',');
            }
            result.append(String.valueOf(item.getItemID()));
            result.append(':');
            result.append(String.valueOf(item.getValue()));
        }
        result.append(']');
        return result.toString();
    }

}