/
FilterIterator.java
90 lines (77 loc) · 2.18 KB
/
FilterIterator.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
/*
* 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.iceberg.io;
import java.io.Closeable;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* An Iterator that filters another Iterator.
*
* @param <T> the type of objects produced by this Iterator
*/
public abstract class FilterIterator<T> implements CloseableIterator<T> {
private final Iterator<T> items;
private boolean closed;
private boolean nextReady;
private T next;
protected FilterIterator(Iterator<T> items) {
this.items = items;
this.closed = false;
this.next = null;
this.nextReady = false;
}
protected abstract boolean shouldKeep(T item);
@Override
public boolean hasNext() {
return nextReady || advance();
}
@Override
public T next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
this.nextReady = false;
return next;
}
private boolean advance() {
while (!closed && items.hasNext()) {
this.next = items.next();
if (shouldKeep(next)) {
this.nextReady = true;
return true;
}
}
close();
this.nextReady = false;
return false;
}
@Override
public void close() {
if (!closed) {
try {
((Closeable) items).close();
} catch (IOException e) {
throw new UncheckedIOException(e);
}
this.closed = true;
}
}
}