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. 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<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") { >
