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This library provides efficient implementations for various collection data structures (esp. linked lists and priority queues), which have very insufficient implementation in the Java Collections Foundations that makes it hard or even impossible to exploit their efficiencies.

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/* Copyright (C) 2013-2023 TU Dortmund
 * This file is part of AutomataLib, http://www.automatalib.net/.
 *
 * 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 net.automatalib.common.smartcollection;

import java.util.AbstractList;
import java.util.Arrays;
import java.util.Collection;
import java.util.RandomAccess;
import java.util.function.Supplier;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A thin wrapper around a simple {@code Object[]} array. Mainly used (and useful) for heavily generic and array-based
 * data storage. Extends/Implements some convenient classes/interfaces.
 *
 * @param 
 *         the type of stored elements
 */
public final class ArrayStorage extends AbstractList implements RandomAccess, Cloneable {

    private final @Nullable Object[] storage;

    public ArrayStorage(int size) {
        this.storage = new Object[size];
    }

    public ArrayStorage(int size, Supplier supplier) {
        this.storage = new Object[size];
        for (int i = 0; i < size; i++) {
            storage[i] = supplier.get();
        }
    }

    public ArrayStorage(Collection collection) {
        storage = collection.toArray();
    }

    private ArrayStorage(@Nullable Object[] storage) {
        this.storage = storage;
    }

    @Override
    @SuppressWarnings("unchecked")
    public T get(int index) {
        return (T) storage[index];
    }

    @Override
    public T set(int index, T element) {
        final T oldValue = get(index);
        storage[index] = element;
        return oldValue;
    }

    @Override
    public int size() {
        return storage.length;
    }

    @SuppressWarnings("PMD.ProperCloneImplementation") //we want to cut cloning hierarchy here
    @Override
    public ArrayStorage clone() {
        return new ArrayStorage<>(storage.clone());
    }

    @Override
    public boolean equals(@Nullable Object o) {
        if (this == o) {
            return true;
        }
        if (!(o instanceof ArrayStorage)) {
            return false;
        }

        final ArrayStorage that = (ArrayStorage) o;
        return Arrays.equals(storage, that.storage);
    }

    @Override
    public int hashCode() {
        return Arrays.hashCode(storage);
    }
}