1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.apache.maven.surefire.api.util;
20
21 import java.util.Iterator;
22 import java.util.NoSuchElementException;
23
24 /**
25 * This iterator is marked as stopped if {@link #isClosed()} returns {@code true}.
26 * If the iterator has been closed before calling {@link #hasNext()} then the method returns {@code false}.
27 * If the iterator was closed after {@link #hasNext() hasNext returns true} but before {@link #next()}, the
28 * method {@link #next()} throws {@link java.util.NoSuchElementException}.
29 * The method {@link #remove()} throws {@link IllegalStateException} if the iterator has been closed.
30 *
31 * @param <T> the type of elements returned by this iterator
32 *
33 * @author <a href="mailto:tibordigana@apache.org">Tibor Digana (tibor17)</a>
34 * @since 2.19.1
35 */
36 public abstract class CloseableIterator<T> implements Iterator<T> {
37 private Boolean finishCurrentIteration;
38
39 protected abstract boolean isClosed();
40
41 protected abstract boolean doHasNext();
42
43 protected abstract T doNext();
44
45 protected abstract void doRemove();
46
47 @Override
48 public boolean hasNext() {
49 popMarker();
50 return !finishCurrentIteration && doHasNext();
51 }
52
53 @Override
54 public T next() {
55 try {
56 if (popMarker() && finishCurrentIteration) {
57 throw new NoSuchElementException("iterator closed");
58 }
59 return doNext();
60 } finally {
61 finishCurrentIteration = null;
62 }
63 }
64
65 @Override
66 public void remove() {
67 try {
68 if (popMarker() && finishCurrentIteration) {
69 throw new IllegalStateException("iterator closed");
70 }
71 doRemove();
72 } finally {
73 finishCurrentIteration = null;
74 }
75 }
76
77 /**
78 * @return {@code true} if marker changed from NULL to anything
79 */
80 private boolean popMarker() {
81 if (finishCurrentIteration == null) {
82 finishCurrentIteration = isClosed();
83 return true;
84 }
85 return false;
86 }
87 }