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Resilience4j is a lightweight, easy-to-use fault tolerance library designed for Java8 and functional programming

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/*
 *
 *  Copyright 2016 Robert Winkler and Bohdan Storozhuk
 *
 *  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.github.resilience4j.circularbuffer;

import io.vavr.collection.List;
import io.vavr.control.Option;

/**
 * A {@link CircularFifoBuffer} is a first in first out buffer with a fixed size that replaces its oldest element if full.
 * {@link CircularFifoBuffer} does NOT accept null elements.
 **/
public interface CircularFifoBuffer {
    /**
     * Returns the number of elements in this {@link CircularFifoBuffer}.
     *
     * @return the number of elements in this {@link CircularFifoBuffer}
     */
    int size();

    /**
     * Returns true if this {@link CircularFifoBuffer} contains no elements.
     *
     * @return true if this {@link CircularFifoBuffer} contains no elements
     */
    boolean isEmpty();

    /**
     * Returns true if this {@link CircularFifoBuffer} is full.
     *
     * @return true if this {@link CircularFifoBuffer} is full
     */
    boolean isFull();

    /**
     * Returns a list containing all of the elements in this {@link CircularFifoBuffer}.
     * The elements are copied into an array.
     *
     * @return a list containing all of the elements in this {@link CircularFifoBuffer}
     */
    List toList();

    /**
     * Adds element to the {@link CircularFifoBuffer}
     * and overwrites the oldest element when {@link CircularFifoBuffer#isFull}.
     *
     * @param element to add
     * @throws NullPointerException if the specified element is null
     */
    void add(T element);

    /**
     * Retrieves and removes the head of this queue,
     * or returns {@link Option.None} if this queue is empty.
     *
     * @return the head of this queue, or {@link Option.None} if this queue is empty
     */
    Option take();
}