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Implement getRandom() for Iterables #3266

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Implement getRandom() for Iterables #3266

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5 changes: 5 additions & 0 deletions guava-tests/test/com/google/common/collect/IterablesTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1440,6 +1440,11 @@ public void testIterables_nullCheck() throws Exception {
.testNulls();
}

public void testGetRandom() {
ArrayList<String> strings = Lists.newArrayList("d", "a", "o");
strings.forEach(string -> assertTrue(strings.contains(Iterables.getRandom(strings))));
}

private static void verifyMergeSorted(
Iterable<Iterable<Integer>> iterables, Iterable<Integer> unsortedExpected) {
Iterable<Integer> expected = Ordering.natural().sortedCopy(unsortedExpected);
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14 changes: 14 additions & 0 deletions guava/src/com/google/common/collect/Iterables.java
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Expand Up @@ -25,6 +25,7 @@
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Function;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
Expand All @@ -34,6 +35,7 @@
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Queue;
import java.util.Random;
import java.util.RandomAccess;
import java.util.Set;
import java.util.Spliterator;
Expand Down Expand Up @@ -1017,6 +1019,18 @@ public Iterator<T> iterator() {
return new UnmodifiableIterable<>(iterable);
}

/**
* Picks up random value from {@link Iterable}.
* <p>
* Consider providing {@link Iterable} with at least 1 element,
* in other way you will get {@link IllegalArgumentException}.
* </p>
*/
public static <T> T getRandom(final Iterable<T> iterable) {
Preconditions.checkNotNull(iterable);
return Iterables.get(iterable, new Random().nextInt(Iterables.size(iterable)));
}

// TODO(user): Is this the best place for this? Move to fluent functions?
// Useful as a public method?
static <T> Function<Iterable<? extends T>, Iterator<? extends T>> toIterator() {
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