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GS Collections is a collections framework for Java. It has JDK-compatible List, Set and Map implementations with a rich API and set of utility classes that work with any JDK compatible Collections, Arrays, Maps or Strings. The iteration protocol was inspired by the Smalltalk collection framework.

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/*
 * Copyright 2015 Goldman Sachs.
 *
 * 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.gs.collections.impl.lazy;

import java.util.Iterator;
import java.util.ListIterator;

import com.gs.collections.api.block.procedure.Procedure;
import com.gs.collections.api.block.procedure.Procedure2;
import com.gs.collections.api.block.procedure.primitive.ObjectIntProcedure;
import com.gs.collections.api.list.ListIterable;
import com.gs.collections.impl.block.factory.Procedures;
import net.jcip.annotations.Immutable;

/**
 * A ReverseIterable is an iterable that wraps another iterable and iterates in reverse order.
 */
@Immutable
public class ReverseIterable
        extends AbstractLazyIterable
{
    private final ListIterable adapted;

    public ReverseIterable(ListIterable newAdapted)
    {
        this.adapted = newAdapted;
    }

    public static  ReverseIterable adapt(ListIterable listIterable)
    {
        return new ReverseIterable(listIterable);
    }

    public void each(Procedure procedure)
    {
        this.adapted.reverseForEach(procedure);
    }

    @Override
    public void forEachWithIndex(ObjectIntProcedure objectIntProcedure)
    {
        this.adapted.reverseForEach(Procedures.fromObjectIntProcedure(objectIntProcedure));
    }

    @Override
    public  void forEachWith(Procedure2 procedure, P parameter)
    {
        this.adapted.reverseForEach(Procedures.bind(procedure, parameter));
    }

    @Override
    public int size()
    {
        return this.adapted.size();
    }

    @Override
    public T getFirst()
    {
        return this.adapted.getLast();
    }

    @Override
    public T getLast()
    {
        return this.adapted.getFirst();
    }

    @Override
    public boolean isEmpty()
    {
        return this.adapted.isEmpty();
    }

    public Iterator iterator()
    {
        ListIterator listIterator = this.adapted.listIterator(this.adapted.size());
        return new ReverseIterator(listIterator);
    }

    private static final class ReverseIterator implements Iterator
    {
        private final ListIterator listIterator;

        private ReverseIterator(ListIterator listIterator)
        {
            this.listIterator = listIterator;
        }

        public boolean hasNext()
        {
            return this.listIterator.hasPrevious();
        }

        public T next()
        {
            return this.listIterator.previous();
        }

        public void remove()
        {
            throw new UnsupportedOperationException("Cannot call remove() on " + this.getClass().getSimpleName());
        }
    }
}