Add Range.overlaps(Range) to test for a nonempty intersection #8649

Original file line number	Diff line number	Diff line change
Expand Up		@@ -122,6 +122,33 @@ public void testIsConnected() {
		assertFalse(Range.closed(3, 5).isConnected(Range.closedOpen(7, 7)));
		}

	public void testOverlaps() {
	// shares one or more values
	assertTrue(Range.closed(3, 5).overlaps(Range.closed(4, 6)));
	assertTrue(Range.closed(3, 5).overlaps(Range.closed(5, 7)));
	assertTrue(Range.closed(3, 5).overlaps(Range.closed(3, 5)));
	assertTrue(Range.closed(3, 5).overlaps(Range.open(2, 4)));
	assertTrue(Range.atLeast(3).overlaps(Range.atMost(3)));
	assertTrue(Range.<Integer>all().overlaps(Range.closed(3, 5)));

	// connected but no shared value
	assertFalse(Range.closed(3, 5).overlaps(Range.open(5, 7)));
	assertFalse(Range.closedOpen(3, 5).overlaps(Range.closed(5, 7)));

	// disconnected
	assertFalse(Range.closed(3, 5).overlaps(Range.closed(7, 9)));
	assertFalse(Range.lessThan(3).overlaps(Range.greaterThan(3)));

	// empty ranges overlap nothing, not even themselves
	assertFalse(Range.closedOpen(4, 4).overlaps(Range.closed(1, 9)));
	assertFalse(Range.closed(1, 9).overlaps(Range.closedOpen(4, 4)));
	assertFalse(Range.closedOpen(4, 4).overlaps(Range.closedOpen(4, 4)));

	// symmetry
	assertTrue(Range.closed(5, 7).overlaps(Range.closed(3, 5)));
	assertFalse(Range.open(5, 7).overlaps(Range.closed(3, 5)));
	}

		private static void checkContains(Range<Integer> range) {
		assertFalse(range.contains(4));
		assertTrue(range.contains(5));
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27 changes: 27 additions & 0 deletions guava/src/com/google/common/collect/Range.java

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -517,6 +517,33 @@ public boolean isConnected(Range<C> other) {
		&& other.lowerBound.compareTo(upperBound) <= 0;
		}

	/**
	* Returns {@code true} if there is at least one value {@linkplain #contains contained} by both
	* this range and {@code other}; equivalently, if this range and {@code other} have a nonempty
	* {@linkplain #intersection intersection}.
	*
	* <p>For example:
	*
	* <ul>
	* <li>{@code [2, 4)} and {@code [5, 7)} do not overlap
	* <li>{@code [2, 4)} and {@code [4, 6)} do not overlap: although they are {@linkplain
	* #isConnected connected}, the only range enclosed by both is empty
	* <li>{@code [2, 4)} and {@code [3, 5)} overlap, because both contain {@code 3}
	* </ul>
	*
	* <p>The overlapping relation is symmetric. It is reflexive except that an {@linkplain #isEmpty
	* empty} range does not overlap any range, not even itself.
	*
	* <p>Note that certain discrete ranges are not considered to overlap even though no elements lie
	* "between them": for example, {@code [3, 5]} does not overlap {@code [6, 10]}. In such cases it
	* may be desirable to preprocess both ranges with {@link #canonical(DiscreteDomain)} first.
	*
	* @since NEXT
	*/
	public boolean overlaps(Range<C> other) {
	return isConnected(other) && !intersection(other).isEmpty();
	}

		/**
		* Returns the maximal range {@linkplain #encloses enclosed} by both this range and {@code
		* connectedRange}, if such a range exists.
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