[LANG-726] Add a method e.g. Range<T> Range<T>.intersectionWith(Range<T>)

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@1147537 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/lang3/Range.java

@@ -371,6 +371,26 @@ public final class Range<T> implements Serializable {
         return isBefore(otherRange.minimum);
     }
 
+    /**
+     * Calculate the intersection of {@code this} and an overlapping Range.
+     * @param other overlapping Range
+     * @return range representing the intersection of {@code this} and {@code other} ({@code this} if equal)
+     * @throws IllegalArgumentException if {@code other} does not overlap {@code this}
+     * @since 3.0.1
+     */
+    public Range<T> intersectionWith(Range<T> other) {
+        if (!this.isOverlappedBy(other)) {
+            throw new IllegalArgumentException(String.format(
+                "Cannot calculate intersection with non-overlapping range %s", other));
+        }
+        if (this.equals(other)) {
+            return this;
+        }
+        T min = getComparator().compare(minimum, other.minimum) < 0 ? other.minimum : minimum;
+        T max = getComparator().compare(maximum, other.maximum) < 0 ? maximum : other.maximum;
+        return between(min, max, getComparator());
+    }
+
     // Basics
     //--------------------------------------------------------------------
 

src/test/java/org/apache/commons/lang3/RangeTest.java

@@ -342,6 +342,27 @@ public class RangeTest {
         assertFalse(intRange.isBeforeRange(Range.between(10, 20)));
     }
 
+    @Test
+    public void testIntersectionWith() {
+        assertSame(intRange, intRange.intersectionWith(intRange));
+        assertSame(byteRange, byteRange.intersectionWith(byteRange));
+        assertSame(longRange, longRange.intersectionWith(longRange));
+        assertSame(floatRange, floatRange.intersectionWith(floatRange));
+        assertSame(doubleRange, doubleRange.intersectionWith(doubleRange));
+
+        assertEquals(Range.between(10, 15), intRange.intersectionWith(Range.between(5, 15)));
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testIntersectionWithNull() {
+        intRange.intersectionWith(null);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testIntersectionWithNonOverlapping() {
+        intRange.intersectionWith(Range.between(0, 9));
+    }
+
     //-----------------------------------------------------------------------
     @Test
     public void testSerializing() {