com.google.uzaygezen.core.MapNode.java Source code

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Here is the source code for com.google.uzaygezen.core.MapNode.java

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/*
 * Copyright (C) 2008 Google Inc.
 *
 * 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.google.uzaygezen.core;

import java.util.ArrayDeque;
import java.util.Collections;
import java.util.Deque;
import java.util.List;
import java.util.Map;

import org.apache.commons.lang3.builder.ReflectionToStringBuilder;
import org.apache.commons.lang3.builder.ToStringStyle;

import com.google.common.base.Objects;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;

/**
 * Unmodifiable tree node. This is the output of the streaming rollup operation.
 * 
 * TODO: Add some unit tests for this class.
 * 
 * @author Daniel Aioanei
 *
 * @param <K> key type
 * @param <V> value type
 */
public class MapNode<K, V> {

    private final V value;
    private final Map<K, MapNode<K, V>> children;

    public static <K, V> MapNode<K, V> create(V value, Map<K, MapNode<K, V>> children) {
        return new MapNode<K, V>(value, children);
    }

    private MapNode(V value, Map<K, MapNode<K, V>> children) {
        this.value = Preconditions.checkNotNull(value, "value");
        // Lame attempt to detect cycles.
        Preconditions.checkArgument(!children.values().contains(this), "I can't be my own child.");
        this.children = Collections.unmodifiableMap(children);
    }

    public V getValue() {
        return value;
    }

    public Map<K, MapNode<K, V>> getChildren() {
        return children;
    }

    /**
     * For testing purposes only.
     * 
     * @return the number of nodes in the subtree rooted in this node and the
     * number of leaves.
     */
    int[] subtreeSizeAndLeafCount() {
        Deque<MapNode<K, V>> stack = new ArrayDeque<MapNode<K, V>>();
        stack.push(this);
        MapNode<K, V> node;
        int size = 0;
        int leafCount = 0;
        while ((node = stack.poll()) != null) {
            ++size;
            if (node.children.isEmpty()) {
                ++leafCount;
            }
            for (MapNode<K, V> child : node.children.values()) {
                stack.push(child);
            }
        }
        return new int[] { size, leafCount };
    }

    /**
     * For testing purposes only.
     * 
     * @return the full preorder list of nodes of this subtree
     */
    public List<MapNode<K, V>> preorder() {
        List<MapNode<K, V>> list = Lists.newArrayList();
        Deque<MapNode<K, V>> stack = new ArrayDeque<MapNode<K, V>>();
        stack.push(this);
        MapNode<K, V> node;
        while ((node = stack.poll()) != null) {
            list.add(node);
            for (MapNode<K, V> child : node.children.values()) {
                stack.push(child);
            }
        }
        return list;
    }

    @Override
    public String toString() {
        return ReflectionToStringBuilder.toString(this, ToStringStyle.SHORT_PREFIX_STYLE);
    }

    /**
     * For testing purposes only.
     */
    @Override
    public int hashCode() {
        return Objects.hashCode(value, children);
    }

    /**
     * For testing purposes only.
     */
    @Override
    public boolean equals(Object o) {
        if (!(o instanceof MapNode<?, ?>)) {
            return false;
        }
        MapNode<?, ?> other = (MapNode<?, ?>) o;
        /*
         * This is the only place where we use equals for value comparison.
         * Everywhere else we use compareTo.
         */
        return value.equals(other.value) && Objects.equal(children, other.children);
    }
}