Shortcut checks for identical objects

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1336985 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/math3/util/Pair.java

@@ -83,6 +83,9 @@ public class Pair<K, V> {
      */
     @Override
     public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
         if (!(o instanceof Pair)) {
             return false;
         } else {