Fixed ReflectiveMethodResolver to avoid potential UnsupportedOperationException on sort

Issue: SPR-10392

spring-expression/src/main/java/org/springframework/expression/spel/support/ReflectiveMethodResolver.java

@@ -103,6 +103,7 @@ public class ReflectiveMethodResolver implements MethodResolver {
 			}
 
 			// Sort methods into a sensible order
+			if (methods.size() > 1) {
 				Collections.sort(methods, new Comparator<Method>() {
 					public int compare(Method m1, Method m2) {
 						int m1pl = m1.getParameterTypes().length;
@@ -110,6 +111,7 @@ public class ReflectiveMethodResolver implements MethodResolver {
 						return (new Integer(m1pl)).compareTo(m2pl);
 					}
 				});
+			}
 
 			// Resolve any bridge methods
 			for (int i = 0; i < methods.size(); i++) {