BoundedLinkedList.java

/*
 *  Copyright 2010 Kevin Gaudin
 *
 *  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 org.acra.collections;

import android.support.annotation.NonNull;

import java.util.Collection;
import java.util.LinkedList;

/**
 * A {@link LinkedList} version with a maximum number of elements. When adding
 * elements to the end of the list, first elements in the list are discarded if
 * the maximum size is reached.
 *
 * @author Kevin Gaudin
 */
@SuppressWarnings("serial")
public final class BoundedLinkedList<E> extends LinkedList<E> {

    private final int maxSize;

    public BoundedLinkedList(int maxSize) {
        this.maxSize = maxSize;
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.LinkedList#add(java.lang.Object)
     */
    @Override
    public boolean add(E object) {
        if (size() == maxSize) {
            removeFirst();
        }
        return super.add(object);
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.LinkedList#add(int, java.lang.Object)
     */
    @Override
    public void add(int location, E object) {
        if (size() == maxSize) {
            removeFirst();
        }
        super.add(location, object);
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.LinkedList#addAll(java.util.Collection)
     */
    @Override
    public boolean addAll(@NonNull Collection<? extends E> collection) {
        final int size = collection.size();
        if (size > maxSize) {
            final LinkedList<? extends E> list = new LinkedList<E>(collection);
            for (int i = 0; i < size - maxSize; i++) {
                list.removeFirst();
            }
            collection = list;
        }
        final int totalNeededSize = size() + collection.size();
        final int overhead = totalNeededSize - maxSize;
        if (overhead > 0) {
            removeRange(0, overhead);
        }
        return super.addAll(collection);
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.LinkedList#addAll(int, java.util.Collection)
     */
    @Override
    public boolean addAll(int location, Collection<? extends E> collection) {
        // int totalNeededSize = size() + collection.size();
        // int overhead = totalNeededSize - maxSize;
        // if(overhead > 0) {
        // removeRange(0, overhead);
        // }
        // return super.addAll(location, collection);
        if(location == size()){
            return super.addAll(location, collection);
        }
        throw new UnsupportedOperationException();
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.LinkedList#addFirst(java.lang.Object)
     */
    @Override
    public void addFirst(E object) {
        // super.addFirst(object);
        throw new UnsupportedOperationException();
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.LinkedList#addLast(java.lang.Object)
     */
    @Override
    public void addLast(E object) {
        add(object);
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.AbstractCollection#toString()
     */
    @NonNull
    @Override
    public String toString() {
        final StringBuilder result = new StringBuilder();
        for (E object : this) {
            result.append(object.toString());
        }
        return result.toString();
    }

    @Override
    public boolean offer(E o) {
        return add(o);
    }

    @Override
    public boolean offerFirst(E e) {
        addFirst(e);
        return true;
    }

    @Override
    public boolean offerLast(E e) {
        return add(e);
    }

    @Override
    public void push(E e) {
        add(e);
    }
}