Improve documentation for SpEL Elvis operator

Author: sbrannen

framework-docs/modules/ROOT/pages/core/expressions/language-ref/operator-elvis.adoc

@@ -2,18 +2,18 @@
 = The Elvis Operator
 
 The Elvis operator is a shortening of the ternary operator syntax and is used in the
-https://www.groovy-lang.org/operators.html#_elvis_operator[Groovy] language.
-With the ternary operator syntax, you usually have to repeat a variable twice, as the
-following example shows:
+https://www.groovy-lang.org/operators.html#_elvis_operator[Groovy] language. With the
+ternary operator syntax, you often have to repeat a variable twice, as the following
+Java example shows:
 
-[source,groovy,indent=0,subs="verbatim,quotes"]
+[source,java,indent=0,subs="verbatim,quotes"]
 ----
 	String name = "Elvis Presley";
 	String displayName = (name != null ? name : "Unknown");
 ----
 
 Instead, you can use the Elvis operator (named for the resemblance to Elvis' hair style).
-The following example shows how to use the Elvis operator:
+The following example shows how to use the Elvis operator in a SpEL expression:
 
 [tabs]
 ======
@@ -38,9 +38,13 @@ Kotlin::
 ----
 ======
 
-NOTE: The SpEL Elvis operator also checks for _empty_ Strings in addition to `null` objects.
-The original snippet is thus only close to emulating the semantics of the operator (it would need an
-additional `!name.isEmpty()` check).
+[NOTE]
+====
+The SpEL Elvis operator also treats an _empty_ String like a `null` object. Thus, the
+original Java example is only close to emulating the semantics of the operator: it would
+need to use `name != null && !name.isEmpty()` as the predicate to be compatible with the
+semantics of the SpEL Elvis operator.
+====
 
 The following listing shows a more complex example:
 
@@ -79,7 +83,7 @@ Kotlin::
 ----
 ======
 
-[NOTE]
+[TIP]
 =====
 You can use the Elvis operator to apply default values in expressions. The following
 example shows how to use the Elvis operator in a `@Value` expression:
@@ -89,7 +93,6 @@ example shows how to use the Elvis operator in a `@Value` expression:
 	@Value("#{systemProperties['pop3.port'] ?: 25}")
 ----
 
-This will inject a system property `pop3.port` if it is defined or 25 if not.
+This will inject the value of the system property named `pop3.port` if it is defined or
+`25` if the property is not defined.
 =====
-
-