JDK 8 code review request for 8011800: Add java.util.Objects.requireNonNull(T, Supplier<String>)

[Joe Darcy]

Hello,

Please review my changes for

     8011800: Add java.util.Objects.requireNonNull(T, Supplier<String>)
     http://cr.openjdk.java.net/~darcy/8011800.0/

which add a new method to java.util.Objects to take a Supplier<String> 
rather than a String.

Patch inline below.

Thanks,

-Joe

--- old/src/share/classes/java/util/Objects.java    2013-04-09 
14:08:34.000000000 -0700
+++ new/src/share/classes/java/util/Objects.java    2013-04-09 
14:08:33.000000000 -0700
@@ -1,5 +1,5 @@
  /*
- * Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights 
reserved.
+ * Copyright (c) 2009, 2013, Oracle and/or its affiliates. All rights 
reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
@@ -25,6 +25,8 @@

  package java.util;

+import java.util.function.Supplier;
+
  /**
   * This class consists of {@code static} utility methods for operating
   * on objects.  These utilities include {@code null}-safe or {@code
@@ -226,4 +228,31 @@
              throw new NullPointerException(message);
          return obj;
      }
+
+    /**
+     * Checks that the specified object reference is not {@code null} and
+     * throws a customized {@link NullPointerException} if it is.
+     *
+     * <p>Compared to the sibling method {@link requireNonNull(Object,
+     * String}, this methods allows creation of the message to be
+     * deferred until after the null check is made. Note that if the
+     * supplier is provided via a lambda expression, there can be an
+     * overhead involved in creating the supplier. Therefore, while
+     * this method may confer a net performance advantage in the
+     * non-null case, it is most likely to do so if creating the
+     * message string is expensive.
+     *
+     * @param obj     the object reference to check for nullity
+     * @param messageSupplier supplier of the detail message to be
+     * used in the event that a {@code NullPointerException} is thrown
+     * @param <T> the type of the reference
+     * @return {@code obj} if not {@code null}
+     * @throws NullPointerException if {@code obj} is {@code null}
+     * @since 1.8
+     */
+    public static <T> T requireNonNull(T obj, Supplier<String> 
messageSupplier) {
+        if (obj == null)
+            throw new NullPointerException(messageSupplier.get());
+        return obj;
+    }
  }
--- old/test/java/util/Objects/BasicObjectsTest.java    2013-04-09 
14:08:34.000000000 -0700
+++ new/test/java/util/Objects/BasicObjectsTest.java    2013-04-09 
14:08:34.000000000 -0700
@@ -1,5 +1,5 @@
  /*
- * Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights 
reserved.
+ * Copyright (c) 2009, 2013, Oracle and/or its affiliates. All rights 
reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
@@ -23,7 +23,7 @@

  /*
   * @test
- * @bug 6797535 6889858 6891113
+ * @bug 6797535 6889858 6891113 8011800
   * @summary Basic tests for methods in java.util.Objects
   * @author  Joseph D. Darcy
   */
@@ -166,17 +166,17 @@
          try {
              s = Objects.requireNonNull("pants");
              if (s != "pants") {
-                System.err.printf("1-arg non-null failed to return its 
arg");
+                System.err.printf("1-arg requireNonNull failed to 
return its arg");
                  errors++;
              }
          } catch (NullPointerException e) {
-            System.err.printf("1-arg nonNull threw unexpected NPE");
+            System.err.printf("1-arg requireNonNull threw unexpected NPE");
              errors++;
          }

          try {
              s = Objects.requireNonNull(null);
-            System.err.printf("1-arg nonNull failed to throw NPE");
+            System.err.printf("1-arg requireNonNull failed to throw NPE");
              errors++;
          } catch (NullPointerException e) {
              // Expected
@@ -186,17 +186,40 @@
          try {
              s = Objects.requireNonNull("pants", "trousers");
              if (s != "pants") {
-                System.err.printf("2-arg nonNull failed to return its 
arg");
+                System.err.printf("2-arg requireNonNull failed to 
return its arg");
                  errors++;
              }
          } catch (NullPointerException e) {
-            System.err.printf("2-arg nonNull threw unexpected NPE");
+            System.err.printf("2-arg requireNonNull threw unexpected NPE");
              errors++;
          }

          try {
              s = Objects.requireNonNull(null, "pantaloons");
-            System.err.printf("2-arg nonNull failed to throw NPE");
+            System.err.printf("2-arg requireNonNull failed to throw NPE");
+            errors++;
+        } catch (NullPointerException e) {
+            if (e.getMessage() != "pantaloons") {
+                System.err.printf("2-arg requireNonNull threw NPE w/ 
bad detail msg");
+                errors++;
+            }
+        }
+
+        // Test supplier rvariant
+        try {
+            s = Objects.requireNonNull("pants", () -> "trousers");
+            if (s != "pants") {
+                System.err.printf("Supplier requireNonNull failed to 
return its arg");
+                errors++;
+            }
+        } catch (NullPointerException e) {
+            System.err.printf("Supplier nonNull threw unexpected NPE");
+            errors++;
+        }
+
+        try {
+            s = Objects.requireNonNull(null, () -> "pantaloons");
+            System.err.printf("Suppiler requireNonNull failed to throw 
NPE");
              errors++;
          } catch (NullPointerException e) {
              if (e.getMessage() != "pantaloons") {