JDK 8 code review request for 8011800: Add java.util.Objects.requireNonNull(T, Supplier) (original) (raw)

Joe Darcy joe.darcy at oracle.com
Wed Apr 10 01:22:03 UTC 2013

On 04/09/2013 06:00 PM, Mike Duigou wrote:

Are we convinced that the capture cost of the lambdas likely to be used as suppliers is generally (*) better than the string construction that using a Supplier would avoid?

(*) I say "generally" because I am certain examples could be found in which either is clearly better.

I know I've hesitated to use the existing requireNonNull method with a custom message at times because of having to always pay the string construction cost.

I think the supplier passed as a lambda combination is on the right side of likely vm optimization attention in the JDK 8 train.

-Joe

Mike On Apr 9 2013, at 14:12 , Joe Darcy wrote:

Hello,

Please review my changes for 8011800: Add java.util.Objects.requireNonNull(T, Supplier) http://cr.openjdk.java.net/~darcy/8011800.0/ which add a new method to java.util.Objects to take a Supplier 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. + * + *

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 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 requireNonNull(T obj, Supplier 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") {

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