common-app-api/src/main/java/org/openecomp/sdc/common/util/StreamUtils.java

   1 /*-
   2  * ============LICENSE_START=======================================================
   3  * SDC
   4  * ================================================================================
   5  * Copyright (C) 2017 AT&T Intellectual Property. All rights reserved.
   6  * ================================================================================
   7  * Licensed under the Apache License, Version 2.0 (the "License");
   8  * you may not use this file except in compliance with the License.
   9  * You may obtain a copy of the License at
  10  *
  11  *      http://www.apache.org/licenses/LICENSE-2.0
  12  *
  13  * Unless required by applicable law or agreed to in writing, software
  14  * distributed under the License is distributed on an "AS IS" BASIS,
  15  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  16  * See the License for the specific language governing permissions and
  17  * limitations under the License.
  18  * ============LICENSE_END=========================================================
  19  */
  20
  21 package org.openecomp.sdc.common.util;
  22
  23 import java.util.ArrayList;
  24 import java.util.List;
  25 import java.util.Spliterator;
  26 import java.util.Spliterators.AbstractSpliterator;
  27 import java.util.function.Consumer;
  28 import java.util.function.Predicate;
  29 import java.util.stream.Stream;
  30 import java.util.stream.StreamSupport;
  31
  32 /**
  33  * Utility Class For Actions On Streams
  34  *
  35  * @author mshitrit
  36  *
  37  */
  38 public final class StreamUtils {
  39         private StreamUtils() {
  40                 throw new UnsupportedOperationException();
  41         }
  42
  43         /**
  44          * Breaks the stream when the predicate is not met.<br>
  45          * Does not evaluate elements after the stream breaks.<br>
  46          * This method evaluates the stream.<br>
  47          *
  48          * @param stream
  49          * @param predicate
  50          * @return
  51          */
  52         public static <T> Stream<T> takeWhilePlusOneNoEval(Stream<T> stream, Predicate<T> predicate) {
  53                 List<T> results = new ArrayList<>();
  54                 Consumer<T> listAdder = results::add;
  55                 stream.map(e -> {
  56                         listAdder.accept(e);
  57                         return e;
  58                 }).filter(e -> !predicate.test(e)).findFirst();
  59                 return results.stream();
  60         }
  61
  62         public static <T> Stream<T> takeWhile(Stream<T> stream, Predicate<T> predicate) {
  63                 return StreamSupport.stream(takeWhile(stream.spliterator(), predicate), false);
  64         }
  65
  66         public static <T> Stream<T> takeWhilePlusOne(Stream<T> stream, Predicate<T> predicate) {
  67                 return StreamSupport.stream(takeWhile(stream.spliterator(), new StopAfterFailPredicate<>(predicate)), false);
  68         }
  69
  70         private static <T> Spliterator<T> takeWhile(Spliterator<T> splitr, Predicate<T> predicate) {
  71                 return new MySplitIterator<>(splitr, predicate);
  72         }
  73
  74         public static class MySplitIterator<T> extends AbstractSpliterator<T> implements Spliterator<T> {
  75                 boolean stillGoing = true;
  76                 private Spliterator<T> innerItr;
  77                 private Predicate<T> innerPred;
  78
  79                 private MySplitIterator(Spliterator<T> splitItr, Predicate<T> pred) {
  80                         super(splitItr.estimateSize(), 0);
  81                         innerItr = splitItr;
  82                         innerPred = pred;
  83                 }
  84
  85                 @Override
  86                 public boolean tryAdvance(Consumer<? super T> action) {
  87                         boolean canAdvance = true;
  88                         if (stillGoing) {
  89                                 stillGoing = innerItr.tryAdvance(createConsumerWrapper(action));
  90                         } else {
  91                                 canAdvance = false;
  92                         }
  93                         return canAdvance;
  94                 }
  95
  96                 private Consumer<? super T> createConsumerWrapper(Consumer<? super T> action) {
  97
  98             return new Consumer<T>() {
  99                 @Override
 100                 public void accept(T t) {
 101                     stillGoing = innerPred.test(t);
 102                     if (stillGoing) {
 103                         action.accept(t);
 104                     }
 105
 106                 }
 107             };
 108                 }
 109
 110         }
 111
 112         public static class StopAfterFailPredicate<T> implements Predicate<T> {
 113                 boolean hasNotFailed;
 114                 Predicate<T> innerPredicate;
 115
 116                 private StopAfterFailPredicate(Predicate<T> pred) {
 117                         hasNotFailed = true;
 118                         innerPredicate = pred;
 119                 };
 120
 121                 @Override
 122                 public boolean test(T t) {
 123                         boolean isPassed;
 124                         if (hasNotFailed) {
 125                                 isPassed = true;
 126                                 hasNotFailed = innerPredicate.test(t);
 127                         } else {
 128                                 isPassed = false;
 129                         }
 130                         return isPassed;
 131                 }
 132
 133         }
 134
 135 }