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'rapiddweller Common' is an open source Java library forked from Databene Commons by Volker Bergmann. It provides extensions to the Java core library by utility classes, abstract concepts and concrete implementations.

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/*
 * Copyright (C) 2004-2015 Volker Bergmann ([email protected]).
 * All rights reserved.
 *
 * 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 com.rapiddweller.common.collection;

import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Counts objects.
 * Created: 14.12.2006 18:03:47
 *
 * @param  the type of the counted elements
 * @author Volker Bergmann
 */
public class ObjectCounter {

  private final Map instances;
  /**
   * The Total count.
   */
  long totalCount;

  /**
   * Instantiates a new Object counter.
   *
   * @param initialCapacity the initial capacity
   */
  public ObjectCounter(int initialCapacity) {
    instances = new HashMap<>(initialCapacity);
    totalCount = 0;
  }

  // interface -------------------------------------------------------------------------------------------------------

  /**
   * Count.
   *
   * @param instance the instance
   */
  public void count(E instance) {
    AtomicInteger counter = instances.get(instance);
    if (counter == null) {
      instances.put(instance, new AtomicInteger(1));
    } else {
      counter.incrementAndGet();
    }
    totalCount++;
  }

  /**
   * Uncount.
   *
   * @param instance the instance
   */
  public void uncount(String instance) {
    AtomicInteger counter = instances.get(instance);
    if (counter == null) {
      throw new IllegalStateException("Cannot uncount: " + instance);
    }
    counter.decrementAndGet();
    totalCount--;
  }

  /**
   * Object set set.
   *
   * @return the set
   */
  public Set objectSet() {
    return instances.keySet();
  }

  /**
   * Gets count.
   *
   * @param instance the instance
   * @return the count
   */
  public int getCount(E instance) {
    AtomicInteger counter = instances.get(instance);
    return (counter != null ? counter.intValue() : 0);
  }

  /**
   * Gets relative count.
   *
   * @param instance the instance
   * @return the relative count
   */
  public double getRelativeCount(E instance) {
    return (double) getCount(instance) / totalCount;
  }

  /**
   * Average count double.
   *
   * @return the double
   */
  public double averageCount() {
    return totalCount / instances.size();
  }

  /**
   * Total count double.
   *
   * @return the double
   */
  public double totalCount() {
    return totalCount;
  }

  /**
   * Gets counts.
   *
   * @return the counts
   */
  public Map getCounts() {
    return instances;
  }

  /**
   * Equal distribution boolean.
   *
   * @param tolerance the tolerance
   * @return the boolean
   */
  public boolean equalDistribution(double tolerance) {
    double average = averageCount();
    Collection counts = instances.values();
    for (AtomicInteger count : counts) {
      if (Math.abs((count.doubleValue() - average) / average) > tolerance) {
        return false;
      }
    }
    return true;
  }

  @Override
  public String toString() {
    StringBuilder buffer = new StringBuilder("[");
    Iterator> iterator = instances.entrySet().iterator();
    if (iterator.hasNext()) {
      Map.Entry entry = iterator.next();
      buffer.append(entry.getKey()).append(':').append(entry.getValue());
    }
    while (iterator.hasNext()) {
      Map.Entry entry = iterator.next();
      buffer.append(", ").append(entry.getKey()).append(':').append(entry.getValue());
    }
    buffer.append(']');
    return buffer.toString();
  }

}