org.apache.calcite.linq4j.Ord.java Source code

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Here is the source code for org.apache.calcite.linq4j.Ord.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.linq4j;

import com.google.common.collect.ImmutableList;

import java.util.AbstractList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.RandomAccess;

/**
 * Pair of an element and an ordinal.
 *
 * @param <E> Element type
 */
public class Ord<E> implements Map.Entry<Integer, E> {
    public final int i;
    public final E e;

    /**
     * Creates an Ord.
     */
    public Ord(int i, E e) {
        this.i = i;
        this.e = e;
    }

    /**
     * Creates an Ord.
     */
    public static <E> Ord<E> of(int n, E e) {
        return new Ord<>(n, e);
    }

    /**
     * Creates an iterable of {@code Ord}s over an iterable.
     */
    public static <E> Iterable<Ord<E>> zip(final Iterable<? extends E> iterable) {
        return new Iterable<Ord<E>>() {
            public Iterator<Ord<E>> iterator() {
                return zip(iterable.iterator());
            }
        };
    }

    /**
     * Creates an iterator of {@code Ord}s over an iterator.
     */
    public static <E> Iterator<Ord<E>> zip(final Iterator<? extends E> iterator) {
        return new Iterator<Ord<E>>() {
            int n = 0;

            public boolean hasNext() {
                return iterator.hasNext();
            }

            public Ord<E> next() {
                return Ord.of(n++, iterator.next());
            }

            public void remove() {
                iterator.remove();
            }
        };
    }

    /**
     * Returns a numbered list based on an array.
     */
    public static <E> List<Ord<E>> zip(final E[] elements) {
        return new OrdArrayList<>(elements);
    }

    /**
     * Returns a numbered list.
     */
    public static <E> List<Ord<E>> zip(final List<? extends E> elements) {
        return elements instanceof RandomAccess ? new OrdRandomAccessList<>(elements) : new OrdList<>(elements);
    }

    /**
     * Iterates over an array in reverse order.
     *
     * <p>Given the array ["a", "b", "c"], returns (2, "c") then (1, "b") then
     * (0, "a").
     */
    public static <E> Iterable<Ord<E>> reverse(E... elements) {
        return reverse(ImmutableList.copyOf(elements));
    }

    /**
     * Iterates over a list in reverse order.
     *
     * <p>Given the list ["a", "b", "c"], returns (2, "c") then (1, "b") then
     * (0, "a").
     */
    public static <E> Iterable<Ord<E>> reverse(Iterable<? extends E> elements) {
        final ImmutableList<E> elementList = ImmutableList.copyOf(elements);
        return new Iterable<Ord<E>>() {
            public Iterator<Ord<E>> iterator() {
                return new Iterator<Ord<E>>() {
                    int i = elementList.size() - 1;

                    public boolean hasNext() {
                        return i >= 0;
                    }

                    public Ord<E> next() {
                        return Ord.of(i, elementList.get(i--));
                    }

                    public void remove() {
                        throw new UnsupportedOperationException("remove");
                    }
                };
            }
        };
    }

    public Integer getKey() {
        return i;
    }

    public E getValue() {
        return e;
    }

    public E setValue(E value) {
        throw new UnsupportedOperationException();
    }

    /** List of {@link Ord} backed by a list of elements. */
    private static class OrdList<E> extends AbstractList<Ord<E>> {
        private final List<? extends E> elements;

        public OrdList(List<? extends E> elements) {
            this.elements = elements;
        }

        public Ord<E> get(int index) {
            return of(index, elements.get(index));
        }

        public int size() {
            return elements.size();
        }
    }

    /** List of {@link Ord} backed by a random-access list of elements. */
    private static class OrdRandomAccessList<E> extends OrdList<E> implements RandomAccess {
        public OrdRandomAccessList(List<? extends E> elements) {
            super(elements);
        }
    }

    /** List of {@link Ord} backed by an array of elements. */
    private static class OrdArrayList<E> extends AbstractList<Ord<E>> implements RandomAccess {
        private final E[] elements;

        public OrdArrayList(E[] elements) {
            this.elements = elements;
        }

        @Override
        public Ord<E> get(int index) {
            return Ord.of(index, elements[index]);
        }

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

// End Ord.java