8155902: DataOuputStream should clarify that it might write primitive…

… types as multiple byte groups

Reviewed-by: alanb, djelinski, lancea, rriggs

src/java.base/share/classes/java/io/DataOutputStream.java

@@ -30,7 +30,10 @@
 /**
  * A data output stream lets an application write primitive Java data
  * types to an output stream in a portable way. An application can
- * then use a data input stream to read the data back in.
+ * then use a data input stream to read the data back in. A data output
+ * stream wraps another output stream and delegates writing bytes to the
+ * write methods of that output stream. Writing data consisting of more than
+ * a single byte may cause several writes to the underlying output stream.
  * <p>
  * A DataOutputStream is not safe for use by multiple concurrent
  * threads. If a DataOutputStream is to be used by more than one