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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 com.rapiddweller.common.MathUtil;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

/**
 * Provides a ring buffer for double values.


 * Created: 25.11.2017 19:27:12
 *
 * @author Volker Bergmann
 * @since 1.0.12
 */
public class DoubleRingBuffer {

  private final double[] buffer;
  private int sampleCount;
  private int cursor;
  private boolean filled;
  private double lastValue;

  /**
   * Instantiates a new Double ring buffer.
   *
   * @param capacity the capacity
   */
  public DoubleRingBuffer(int capacity) {
    this.buffer = new double[capacity];
    Arrays.fill(this.buffer, Double.NaN);
    this.sampleCount = 0;
    this.cursor = 0;
    this.filled = false;
  }

  /**
   * Gets sample count.
   *
   * @return the sample count
   */
  public int getSampleCount() {
    return sampleCount;
  }

  /**
   * Gets capacity.
   *
   * @return the capacity
   */
  public int getCapacity() {
    return buffer.length;
  }

  /**
   * Size int.
   *
   * @return the int
   */
  public int size() {
    return buffer.length;
  }

  /**
   * Is filled boolean.
   *
   * @return the boolean
   */
  public boolean isFilled() {
    return filled;
  }

  /**
   * Add.
   *
   * @param value the value
   */
  public void add(double value) {
    lastValue = value;
    this.sampleCount++;
    this.buffer[cursor++] = value;
    if (cursor == buffer.length) {
      filled = true;
      cursor = 0;
    }
  }

  /**
   * Last double.
   *
   * @return the double
   */
  public double last() {
    return lastValue;
  }

  /**
   * First double.
   *
   * @return the double
   */
  public double first() {
    return this.buffer[cursor];
  }

  /**
   * Min double.
   *
   * @return the minimum value in the buffer or NaN if the buffer is empty
   */
  public double min() {
    double min = buffer[0];
    int n = (filled ? buffer.length : cursor);
    for (int i = 1; i < n; i++) {
      if (!Double.isNaN(buffer[i]) && buffer[i] < min) {
        min = buffer[i];
      }
    }
    return min;
  }

  /**
   * Max double.
   *
   * @return the maximum value in the buffer or NaN if the buffer is empty
   */
  public double max() {
    double max = buffer[0];
    int n = (filled ? buffer.length : cursor);
    for (int i = 1; i < n; i++) {
      if (!Double.isNaN(buffer[i]) && buffer[i] > max) {
        max = buffer[i];
      }
    }
    return max;
  }

  /**
   * Average double.
   *
   * @return the double
   */
  public double average() {
    boolean contentFound = false;
    double sum = 0.;
    int count = 0;
    for (double d : buffer) {
      if (!Double.isNaN(d)) {
        contentFound = true;
        sum += d;
        count++;
      }
    }
    return (contentFound ? sum / count : Double.NaN);
  }

  /**
   * Median double.
   *
   * @return the double
   */
  public double median() {
    List list = new ArrayList<>();
    for (double d : buffer) {
      if (!Double.isNaN(d)) {
        list.add(d);
      }
    }
    if (list.isEmpty()) {
      return Double.NaN;
    }
    Collections.sort(list);
    return list.get(list.size() / 2);
  }

  /**
   * Sum double.
   *
   * @return the double
   */
  public double sum() {
    double sum = 0.;
    for (double d : buffer) {
      if (!Double.isNaN(d)) {
        sum += d;
      }
    }
    return sum;
  }

  /**
   * Get content double [ ].
   *
   * @return the double [ ]
   */
  public double[] getContent() {
    return buffer;
  }

  /**
   * Corrected standard deviation double.
   *
   * @return the double
   */
  public double correctedStandardDeviation() {
    if (!filled) {
      return Double.NaN;
    }
    return MathUtil.correctedStandardDeviation(buffer);
  }

  /**
   * Standard deviation double.
   *
   * @return the double
   */
  public double standardDeviation() {
    if (!filled) {
      return Double.NaN;
    }
    return MathUtil.standardDeviation(buffer);
  }

  /**
   * Variance double.
   *
   * @return the double
   */
  public double variance() {
    if (!filled) {
      return Double.NaN;
    }
    return MathUtil.variance(buffer);
  }

}