org.apache.hadoop.io.MapWritable.java Source code

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Here is the source code for org.apache.hadoop.io.MapWritable.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.hadoop.io;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.util.ReflectionUtils;

/**
 * A Writable Map.
 */
@InterfaceAudience.Public
@InterfaceStability.Stable
public class MapWritable extends AbstractMapWritable implements Map<Writable, Writable> {

    private Map<Writable, Writable> instance;

    /** Default constructor. */
    public MapWritable() {
        super();
        this.instance = new HashMap<Writable, Writable>();
    }

    /**
     * Copy constructor.
     * 
     * @param other the map to copy from
     */
    public MapWritable(MapWritable other) {
        this();
        copy(other);
    }

    @Override
    public void clear() {
        instance.clear();
    }

    @Override
    public boolean containsKey(Object key) {
        return instance.containsKey(key);
    }

    @Override
    public boolean containsValue(Object value) {
        return instance.containsValue(value);
    }

    @Override
    public Set<Map.Entry<Writable, Writable>> entrySet() {
        return instance.entrySet();
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }

        if (obj instanceof MapWritable) {
            MapWritable map = (MapWritable) obj;
            if (size() != map.size()) {
                return false;
            }

            return entrySet().equals(map.entrySet());
        }

        return false;
    }

    @Override
    public Writable get(Object key) {
        return instance.get(key);
    }

    @Override
    public int hashCode() {
        return 1 + this.instance.hashCode();
    }

    @Override
    public boolean isEmpty() {
        return instance.isEmpty();
    }

    @Override
    public Set<Writable> keySet() {
        return instance.keySet();
    }

    @Override
    public Writable put(Writable key, Writable value) {
        addToMap(key.getClass());
        addToMap(value.getClass());
        return instance.put(key, value);
    }

    @Override
    public void putAll(Map<? extends Writable, ? extends Writable> t) {
        for (Map.Entry<? extends Writable, ? extends Writable> e : t.entrySet()) {
            put(e.getKey(), e.getValue());
        }
    }

    @Override
    public Writable remove(Object key) {
        return instance.remove(key);
    }

    @Override
    public int size() {
        return instance.size();
    }

    @Override
    public Collection<Writable> values() {
        return instance.values();
    }

    // Writable

    @Override
    public void write(DataOutput out) throws IOException {
        super.write(out);

        // Write out the number of entries in the map

        out.writeInt(instance.size());

        // Then write out each key/value pair

        for (Map.Entry<Writable, Writable> e : instance.entrySet()) {
            out.writeByte(getId(e.getKey().getClass()));
            e.getKey().write(out);
            out.writeByte(getId(e.getValue().getClass()));
            e.getValue().write(out);
        }
    }

    @Override
    public void readFields(DataInput in) throws IOException {
        super.readFields(in);

        // First clear the map.  Otherwise we will just accumulate
        // entries every time this method is called.
        this.instance.clear();

        // Read the number of entries in the map

        int entries = in.readInt();

        // Then read each key/value pair

        for (int i = 0; i < entries; i++) {
            Writable key = (Writable) ReflectionUtils.newInstance(getClass(in.readByte()), getConf());

            key.readFields(in);

            Writable value = (Writable) ReflectionUtils.newInstance(getClass(in.readByte()), getConf());

            value.readFields(in);
            instance.put(key, value);
        }
    }

    @Override
    public String toString() {
        return instance.toString();
    }
}