--- a/src/java.base/share/classes/java/lang/System.java	Thu May 23 10:06:37 2019 -0700
+++ b/src/java.base/share/classes/java/lang/System.java	Thu Jun 06 10:01:36 2019 -0700
@@ -618,8 +618,9 @@
      * {@link #getProperty(String)} method is returned as a
      * {@code Properties} object. If there is no current set of
      * system properties, a set of system properties is first created and
-     * initialized. This set of system properties always includes values
-     * for the following keys:
+     * initialized. This set of system properties includes a value
+     * for each of the following keys unless the description of the associated
+     * value indicates that the value is optional.
      * <table class="striped" style="text-align:left">
      * <caption style="display:none">Shows property keys and associated values</caption>
      * <thead>
@@ -639,7 +640,7 @@
      * <tr><th scope="row">{@systemProperty java.vendor.url}</th>
      *     <td>Java vendor URL</td></tr>
      * <tr><th scope="row">{@systemProperty java.vendor.version}</th>
-     *     <td>Java vendor version</td></tr>
+     *     <td>Java vendor version <em>(optional)</em> </td></tr>
      * <tr><th scope="row">{@systemProperty java.home}</th>
      *     <td>Java installation directory</td></tr>
      * <tr><th scope="row">{@systemProperty java.vm.specification.version}</th>