io.druid.collections.CountingMap.java Source code

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Here is the source code for io.druid.collections.CountingMap.java

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/*
 * Druid - a distributed column store.
 * Copyright 2012 - 2015 Metamarkets Group Inc.
 *
 * Licensed 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 io.druid.collections;

import com.google.common.base.Supplier;
import com.google.common.collect.ImmutableMap;
import com.metamx.common.guava.DefaultingHashMap;

import java.util.Map;
import java.util.concurrent.atomic.AtomicLong;

/**
 */
public class CountingMap<K> extends DefaultingHashMap<K, AtomicLong> {
    public CountingMap() {
        super(new Supplier<AtomicLong>() {
            @Override
            public AtomicLong get() {
                return new AtomicLong(0);
            }
        });
    }

    public long add(K key, long value) {
        return get(key).addAndGet(value);
    }

    public Map<K, Long> snapshot() {
        final ImmutableMap.Builder<K, Long> builder = ImmutableMap.builder();

        for (Map.Entry<K, AtomicLong> entry : entrySet()) {
            builder.put(entry.getKey(), entry.getValue().get());
        }

        return builder.build();
    }
}