src/java.base/share/classes/java/lang/String.java

@@ -76,13 +76,14 @@
  * lowercase. Case mapping is based on the Unicode Standard version
  * specified by the {@link java.lang.Character Character} class.
  * <p>
  * The Java language provides special support for the string
  * concatenation operator (&nbsp;+&nbsp;), and for conversion of
- * other objects to strings. String concatenation is implemented
- * through the {@code StringBuilder}(or {@code StringBuffer})
- * class and its {@code append} method.
+ * other objects to strings. At the discretion of Java compiler,
+ * String concatenation may be implemented through any JDK API, e.g.
+ * the {@code StringBuilder} or the {@code java.lang.invoke.StringConcatFactory},
+ * as long as it satisfies the requirements of the <i>The Java Language Specification</i>.
  * String conversions are implemented through the method
  * {@code toString}, defined by {@code Object} and
  * inherited by all classes in Java. For additional information on
  * string concatenation and conversion, see Gosling, Joy, and Steele,
  * <i>The Java Language Specification</i>.