Counter.java Source code

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Here is the source code for Counter.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.
 */

import java.io.IOException;
import java.io.DataInput;
import java.io.DataOutput;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableUtils;

/**
 * A named counter that tracks the progress of a map/reduce job.
 * 
 * <p><code>Counters</code> represent global counters, defined either by the 
 * Map-Reduce framework or applications. Each <code>Counter</code> is named by
 * an {@link Enum} and has a long for the value.</p>
 * 
 * <p><code>Counters</code> are bunched into Groups, each comprising of
 * counters from a particular <code>Enum</code> class. 
 */
public class Counter implements Writable {

    private String name;
    private String displayName;
    private long value = 0;

    protected Counter() {
    }

    protected Counter(String name, String displayName) {
        this.name = name;
        this.displayName = displayName;
    }

    @Deprecated
    protected synchronized void setDisplayName(String displayName) {
        this.displayName = displayName;
    }

    /**
     * Read the binary representation of the counter
     */
    @Override
    public synchronized void readFields(DataInput in) throws IOException {
        name = Text.readString(in);
        if (in.readBoolean()) {
            displayName = Text.readString(in);
        } else {
            displayName = name;
        }
        value = WritableUtils.readVLong(in);
    }

    /**
     * Write the binary representation of the counter
     */
    @Override
    public synchronized void write(DataOutput out) throws IOException {
        Text.writeString(out, name);
        boolean distinctDisplayName = !name.equals(displayName);
        out.writeBoolean(distinctDisplayName);
        if (distinctDisplayName) {
            Text.writeString(out, displayName);
        }
        WritableUtils.writeVLong(out, value);
    }

    public synchronized String getName() {
        return name;
    }

    /**
     * Get the name of the counter.
     * @return the user facing name of the counter
     */
    public synchronized String getDisplayName() {
        return displayName;
    }

    /**
     * What is the current value of this counter?
     * @return the current value
     */
    public synchronized long getValue() {
        return value;
    }

    /**
     * Increment this counter by the given value
     * @param incr the value to increase this counter by
     */
    public synchronized void increment(long incr) {
        value += incr;
    }

    @Override
    public synchronized boolean equals(Object genericRight) {
        if (genericRight instanceof Counter) {
            synchronized (genericRight) {
                Counter right = (Counter) genericRight;
                return name.equals(right.name) && displayName.equals(right.displayName) && value == right.value;
            }
        }
        return false;
    }

    @Override
    public synchronized int hashCode() {
        return name.hashCode() + displayName.hashCode();
    }
}