[3147] | 1 | // License: GPL. For details, see LICENSE file.
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[3801] | 2 | package org.openstreetmap.josm.tools;
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[3147] | 3 |
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| 4 | import java.util.AbstractCollection;
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| 5 | import java.util.Collection;
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| 6 | import java.util.Iterator;
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| 7 |
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[3801] | 8 | /**
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| 9 | * Filtered view of a collection.
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| 10 | * (read-only collection, but elements can be changed, of course)
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| 11 | * Lets you iterate through those elements of a given collection that satisfy a
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| 12 | * certain condition (imposed by a predicate).
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| 13 | * @param <S> element type of the underlying collection
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| 14 | * @param <T> element type of filtered collection (and subclass of S). The predicate
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[3836] | 15 | * must accept only objects of type T.
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[7395] | 16 | * @since 3147
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[3801] | 17 | */
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| 18 | public class SubclassFilteredCollection<S, T extends S> extends AbstractCollection<T> {
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[3147] | 19 |
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[3801] | 20 | private final Collection<? extends S> collection;
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| 21 | private final Predicate<? super S> predicate;
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[8285] | 22 | private int size = -1;
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[3177] | 23 |
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[3207] | 24 | private class FilterIterator implements Iterator<T> {
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[3147] | 25 |
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[3801] | 26 | private final Iterator<? extends S> iterator;
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| 27 | private S current;
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[3147] | 28 |
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[8836] | 29 | FilterIterator(Iterator<? extends S> iterator) {
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[3147] | 30 | this.iterator = iterator;
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| 31 | }
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| 32 |
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| 33 | private void findNext() {
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| 34 | if (current == null) {
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| 35 | while (iterator.hasNext()) {
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| 36 | current = iterator.next();
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[3177] | 37 | if (predicate.evaluate(current))
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[3147] | 38 | return;
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| 39 | }
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| 40 | current = null;
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| 41 | }
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| 42 | }
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| 43 |
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[6084] | 44 | @Override
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[3147] | 45 | public boolean hasNext() {
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| 46 | findNext();
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| 47 | return current != null;
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| 48 | }
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| 49 |
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[6792] | 50 | @SuppressWarnings("unchecked")
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[6084] | 51 | @Override
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[3207] | 52 | public T next() {
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[3147] | 53 | findNext();
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[3801] | 54 | S old = current;
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[3147] | 55 | current = null;
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[3836] | 56 | // we are save because predicate only accepts objects of type T
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[6792] | 57 | return (T) old;
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[3147] | 58 | }
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| 59 |
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[6084] | 60 | @Override
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[3147] | 61 | public void remove() {
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| 62 | throw new UnsupportedOperationException();
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| 63 | }
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| 64 | }
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| 65 |
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[7395] | 66 | /**
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| 67 | * Constructs a new {@code SubclassFilteredCollection}.
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| 68 | * @param collection The base collection to filter
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| 69 | * @param predicate The predicate to use as filter
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| 70 | */
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[3801] | 71 | public SubclassFilteredCollection(Collection<? extends S> collection, Predicate<? super S> predicate) {
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| 72 | this.collection = collection;
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[3177] | 73 | this.predicate = predicate;
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[3147] | 74 | }
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| 75 |
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| 76 | @Override
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[3207] | 77 | public Iterator<T> iterator() {
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[3801] | 78 | return new FilterIterator(collection.iterator());
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[3147] | 79 | }
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| 80 |
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| 81 | @Override
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| 82 | public int size() {
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[3416] | 83 | if (size == -1) {
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| 84 | size = 0;
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| 85 | Iterator<T> it = iterator();
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| 86 | while (it.hasNext()) {
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| 87 | size++;
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| 88 | it.next();
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| 89 | }
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[3147] | 90 | }
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| 91 | return size;
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| 92 | }
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| 93 |
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| 94 | @Override
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| 95 | public boolean isEmpty() {
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| 96 | return !iterator().hasNext();
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| 97 | }
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[3177] | 98 | }
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