LANG-1485 : Add getters for lhs and rhs objects in DiffResult (#451)

* LANG-1485 : Add getters for lhs and rhs objects in DiffResult

* add @since and rename getters to getLeft and getRight

* fix typo on @since tag

src/main/java/org/apache/commons/lang3/builder/DiffResult.java

@@ -88,6 +88,26 @@ public class DiffResult implements Iterable<Diff<?>> {
         }
     }
 
+    /**
+     * <p>Returns the object the right object has been compared to.</p>
+     *
+     * @return the left object of the diff
+     * @since 3.10
+     */
+    public Object getLeft() {
+        return this.lhs;
+    }
+
+    /**
+     * <p>Returns the object the left object has been compared to.</p>
+     *
+     * @return the right object of the diff
+     * @since 3.10
+     */
+    public Object getRight() {
+        return this.rhs;
+    }
+
     /**
      * <p>
      * Returns an unmodifiable list of {@code Diff}s. The list may be empty if

src/test/java/org/apache/commons/lang3/builder/DiffResultTest.java

@@ -146,4 +146,16 @@ public void testNoDifferencesString() {
                 SHORT_STYLE).build();
         assertEquals(DiffResult.OBJECTS_SAME_STRING, diffResult.toString());
     }
+
+    @Test
+    public void testLeftAndRightGetters() {
+        final SimpleClass left = new SimpleClass(true);
+        final SimpleClass right = new SimpleClass(false);
+
+        final List<Diff<?>> diffs = left.diff(right).getDiffs();
+        final DiffResult diffResult = new DiffResult(left, right, diffs, SHORT_STYLE);
+
+        assertEquals(left, diffResult.getLeft());
+        assertEquals(right, diffResult.getRight());
+    }
 }