org.apache.calcite.util.CompositeList.java Source code

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Here is the source code for org.apache.calcite.util.CompositeList.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you 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.apache.calcite.util;

import com.google.common.collect.ImmutableList;

import java.util.AbstractList;
import java.util.List;

/**
 * Read-only list that is the concatenation of sub-lists.
 *
 * <p>The list is read-only; attempts to call methods such as
 * {@link #add(Object)} or {@link #set(int, Object)} will throw.
 *
 * <p>Changes to the backing lists, including changes in length, will be
 * reflected in this list.
 *
 * <p>This class is not thread-safe. Changes to backing lists will cause
 * unspecified behavior.
 *
 * @param <T> Element type
 */
public class CompositeList<T> extends AbstractList<T> {
    private final ImmutableList<List<T>> lists;

    /**
     * Creates a CompositeList.
     *
     * @param lists Constituent lists
     */
    private CompositeList(ImmutableList<List<T>> lists) {
        this.lists = lists;
    }

    /**
     * Creates a CompositeList.
     *
     * @param lists Constituent lists
     * @param <T>   Element type
     * @return List consisting of all lists
     */
    @SafeVarargs
    public static <T> CompositeList<T> of(List<? extends T>... lists) {
        //noinspection unchecked
        return new CompositeList<T>((ImmutableList) ImmutableList.copyOf(lists));
    }

    /**
     * Creates a CompositeList.
     *
     * @param lists Constituent lists
     * @param <T>   Element type
     * @return List consisting of all lists
     */
    public static <T> CompositeList<T> ofCopy(Iterable<List<T>> lists) {
        final ImmutableList<List<T>> list = ImmutableList.copyOf(lists);
        return new CompositeList<T>(list);
    }

    /**
     * Creates a CompositeList of zero lists.
     *
     * @param <T>   Element type
     * @return List consisting of all lists
     */
    public static <T> List<T> of() {
        return ImmutableList.of();
    }

    /**
     * Creates a CompositeList of one list.
     *
     * @param list0 List
     * @param <T>   Element type
     * @return List consisting of all lists
     */
    public static <T> List<T> of(List<T> list0) {
        return list0;
    }

    /**
     * Creates a CompositeList of two lists.
     *
     * @param list0 First list
     * @param list1 Second list
     * @param <T>   Element type
     * @return List consisting of all lists
     */
    public static <T> CompositeList<T> of(List<? extends T> list0, List<? extends T> list1) {
        //noinspection unchecked
        return new CompositeList<T>((ImmutableList) ImmutableList.of(list0, list1));
    }

    /**
     * Creates a CompositeList of three lists.
     *
     * @param list0 First list
     * @param list1 Second list
     * @param list2 Third list
     * @param <T>   Element type
     * @return List consisting of all lists
     */
    public static <T> CompositeList<T> of(List<? extends T> list0, List<? extends T> list1,
            List<? extends T> list2) {
        //noinspection unchecked
        return new CompositeList<T>((ImmutableList) ImmutableList.of(list0, list1, list2));
    }

    public T get(int index) {
        for (List<? extends T> list : lists) {
            int nextIndex = index - list.size();
            if (nextIndex < 0) {
                return list.get(index);
            }
            index = nextIndex;
        }
        throw new IndexOutOfBoundsException();
    }

    public int size() {
        int n = 0;
        for (List<? extends T> list : lists) {
            n += list.size();
        }
        return n;
    }
}

// End CompositeList.java