diff -r e10a1f7aaa13 -r 8bf9268df0e2 src/java.base/share/classes/javax/security/auth/callback/NameCallback.java
--- a/src/java.base/share/classes/javax/security/auth/callback/NameCallback.java	Thu Dec 13 16:14:07 2018 +0100
+++ b/src/java.base/share/classes/javax/security/auth/callback/NameCallback.java	Thu Dec 13 15:31:05 2018 +0100
@@ -62,7 +62,7 @@
      *                  or if {@code prompt} has a length of 0.
      */
     public NameCallback(String prompt) {
-        if (prompt == null || prompt.length() == 0)
+        if (prompt == null || prompt.isEmpty())
             throw new IllegalArgumentException();
         this.prompt = prompt;
     }
@@ -82,8 +82,8 @@
      *                  or if {@code defaultName} has a length of 0.
      */
     public NameCallback(String prompt, String defaultName) {
-        if (prompt == null || prompt.length() == 0 ||
-            defaultName == null || defaultName.length() == 0)
+        if (prompt == null || prompt.isEmpty() ||
+            defaultName == null || defaultName.isEmpty())
             throw new IllegalArgumentException();
 
         this.prompt = prompt;