JDK 8 code review request for 8011800: Add java.util.Objects.requireNonNull(T, Supplier<String>)
Joe Darcy
joe.darcy at oracle.com
Wed Apr 10 06:06:16 UTC 2013
Hi David,
On 04/09/2013 07:38 PM, David Holmes wrote:
> Hi Joe,
>
> On 10/04/2013 7:12 AM, 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.
>
> I'm not sure the discussion of the potential cost of a lambda
> expression really belongs in the API docs for this method.
The cautionary note could be summarized / expanded as "make sure you
think this is a good idea." Off-list, Brian expressed some concerns
similar to the ones Mike raised about whether or not the method could be
an attractive nuisance if overused so I think some kind of warning is
warranted if the method is included.
-Joe
>
> David
> -----
>
>> 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") {
>>
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