Added empty string example for isMixedCase method.
diff --git a/src/main/java/org/apache/commons/lang3/StringUtils.java b/src/main/java/org/apache/commons/lang3/StringUtils.java
index 0b6fed6..0f58951 100644
--- a/src/main/java/org/apache/commons/lang3/StringUtils.java
+++ b/src/main/java/org/apache/commons/lang3/StringUtils.java
@@ -3605,6 +3605,7 @@
* <pre>
* StringUtils.isMixedCase(null) = false
* StringUtils.isMixedCase("") = false
+ * StringUtils.isMixedCase(" ") = false
* StringUtils.isMixedCase("ABC") = false
* StringUtils.isMixedCase("abc") = false
* StringUtils.isMixedCase("aBc") = true