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small improvements for collectionUtils #17

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izebit wants to merge 3 commits into from
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small improvements for collectionUtils #17

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0dff24d
small improvements for collectionUtils
izebit Jul 28, 2016
aa6b4cc
applied changes after code review
May 22, 2017
9b4e2ef
removed not necessary suppressWarning annotation
izebit May 23, 2017
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21 changes: 7 additions & 14 deletions src/main/java/org/apache/commons/collections4/CollectionUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,12 +19,12 @@
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
Expand Down Expand Up @@ -180,8 +180,7 @@ public Collection<O> list() {
* undesirable. This implementation only implements Collection.
*/
@SuppressWarnings("rawtypes") // we deliberately use the raw type here
public static final Collection EMPTY_COLLECTION =
UnmodifiableCollection.unmodifiableCollection(new ArrayList<Object>());
public static final Collection EMPTY_COLLECTION = Collections.emptyList();
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@kinow kinow May 21, 2017

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Nice catch!

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@izebit izebit May 22, 2017

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:))


/**
* <code>CollectionUtils</code> should not normally be instantiated.
Expand Down Expand Up @@ -209,9 +208,8 @@ public static <T> Collection<T> emptyCollection() {
* @param collection the collection, possibly <code>null</code>
* @return an empty collection if the argument is <code>null</code>
*/
@SuppressWarnings("unchecked") // OK, empty collection is compatible with any type
public static <T> Collection<T> emptyIfNull(final Collection<T> collection) {
return collection == null ? EMPTY_COLLECTION : collection;
return collection == null ? CollectionUtils.<T>emptyCollection() : collection;
}

/**
Expand Down Expand Up @@ -389,9 +387,7 @@ public static boolean containsAll(final Collection<?> coll1, final Collection<?>
}
}

if (foundCurrentElement) {
continue;
} else {
if (!foundCurrentElement) {
return false;
}
}
Expand Down Expand Up @@ -830,7 +826,7 @@ public static <C> int countMatches(final Iterable<C> input, final Predicate<? su
*/
@Deprecated
public static <C> boolean exists(final Iterable<C> input, final Predicate<? super C> predicate) {
return predicate == null ? false : IterableUtils.matchesAny(input, predicate);
return predicate != null && IterableUtils.matchesAny(input, predicate);
}

/**
Expand All @@ -850,7 +846,7 @@ public static <C> boolean exists(final Iterable<C> input, final Predicate<? supe
*/
@Deprecated
public static <C> boolean matchesAll(final Iterable<C> input, final Predicate<? super C> predicate) {
return predicate == null ? false : IterableUtils.matchesAll(input, predicate);
return predicate != null && IterableUtils.matchesAll(input, predicate);
}

/**
Expand Down Expand Up @@ -1266,9 +1262,6 @@ public static Object get(final Object object, final int index) {
} else if (object instanceof Iterable<?>) {
final Iterable<?> iterable = (Iterable<?>) object;
return IterableUtils.get(iterable, i);
} else if (object instanceof Collection<?>) {
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@kinow kinow May 21, 2017

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Is this one really safe to remove? It seems to assume that the else condition will handle with the same behaviour, but I have not tested it to confirm.

Might be worth also moving that if (object == null) check to the top.

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@izebit izebit May 22, 2017 •
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Removing of this condition is safe. Moreover, this check is useless, because, any collection implements interface Iterable, and if object is Collection, then previous condition (object instanceof Iterable<?>) is true.

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@kinow kinow May 22, 2017

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Nice. Will check out the code to review with the IDE, plus some coffee 💤 I think it looks good to be merged. Thanks for the quick replies @izebit

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@kinow kinow May 23, 2017

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Oooohh, just re-read, and finally understood. Sorry, nice catch again.

final Iterator<?> iterator = ((Collection<?>) object).iterator();
return IteratorUtils.get(iterator, i);
} else if (object instanceof Enumeration<?>) {
final Enumeration<?> it = (Enumeration<?>) object;
return EnumerationUtils.get(it, i);
Expand Down Expand Up @@ -1631,7 +1624,7 @@ public static <O> List<O> collate(final Iterable<? extends O> a, final Iterable<
*/
public static <E> Collection<List<E>> permutations(final Collection<E> collection) {
final PermutationIterator<E> it = new PermutationIterator<E>(collection);
final Collection<List<E>> result = new LinkedList<List<E>>();
final Collection<List<E>> result = new ArrayList<List<E>>();
while (it.hasNext()) {
result.add(it.next());
}
Expand Down