common/org.eclipse.tracecompass.common.core/src/org/eclipse/tracecompass/common/core/collect/StreamFlattener.java

   1 /*******************************************************************************
   2  * Copyright (c) 2015 EfficiOS Inc., Alexandre Montplaisir
   3  *
   4  * All rights reserved. This program and the accompanying materials
   5  * are made available under the terms of the Eclipse Public License v1.0
   6  * which accompanies this distribution, and is available at
   7  * http://www.eclipse.org/legal/epl-v10.html
   8  *******************************************************************************/
   9
  10 package org.eclipse.tracecompass.common.core.collect;
  11
  12 import java.util.function.Function;
  13 import java.util.stream.Stream;
  14
  15 /**
  16  * Generic utility class to "flatten" a data structure using the {@link Stream}
  17  * API.
  18  *
  19  * @author Alexandre Montplaisir
  20  *
  21  * @param <T>
  22  *            The type of container, or "node" in the tree
  23  * @since 2.0
  24  */
  25 public class StreamFlattener<T> {
  26
  27     private final Function<T, Stream<T>> fGetChildrenFunction;
  28
  29     /**
  30      * Constructor
  31      *
  32      * @param getChildrenFunction
  33      *            The function to use to get each element's children. Should
  34      *            return a {@link Stream} of those children.
  35      */
  36     public StreamFlattener(Function<T, Stream<T>> getChildrenFunction) {
  37         fGetChildrenFunction = getChildrenFunction;
  38     }
  39
  40     /**
  41      * Do an in-order flattening of the data structure, starting at the given
  42      * element (or node).
  43      *
  44      * @param element
  45      *            The tree node or similar from which to start
  46      * @return A unified Stream of all the children that were found,
  47      *         recursively.
  48      */
  49     public Stream<T> flatten(T element) {
  50         return Stream.concat(
  51                 Stream.of(element),
  52                 fGetChildrenFunction.apply(element).flatMap(this::flatten));
  53     }
  54 }