blocks|key|1158560|text|在if语句中，应该在Objects.isNull()上使用object+Objects.isNull+null吗？|type|blockquote|depth|inlineStyleRanges|entityRanges|data|1158561|如果您查看源代码+of+IsNull方法，|unstyled|offset|length|style|CODE|1158562|+/*+Returns+true+if+the+provided+reference+is+null+otherwise+returns+false.*/

+public+static+boolean+isNull(Object+obj)+{
+++++return+obj+==+null;
+}|code-block|syntax|javascript|1158563|这是一样的。没有什么不同。这样你才能安全地使用它。|1158564|entityMap|0|LINK|mutability|MUTABLE|url|http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/8-b132/java/util/Objects.java#Objects.isNull%2528java.lang.Object%2529^0|0|C|6|5|3|0|0|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Y|8|@$E|Z|F|10|G|H]]|9|@$E|11|F|12|1|13]]|A|$]]|$1|I|3|J|5|K|7|14|8|@]|9|@]|A|$L|M]]|$1|N|3|O|5|D|7|15|8|@]|9|@]|A|$]]|$1|P|3|-4|5|D|7|16|8|@]|9|@]|A|$]]]|Q|$R|$5|S|T|U|A|$V|W]]]]

<blockquote>
 should use object == null over Objects.isNull() in a if statement?
</blockquote>

If you look at the <a href="http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/8-b132/java/util/Objects.java#Objects.isNull%28java.lang.Object%29" rel="noreferrer">source code</a> of <code>IsNull</code> method,

<pre><code> /* Returns true if the provided reference is null otherwise returns false.*/

 public static boolean isNull(Object obj) {
 return obj == null;
 }
</code></pre>

It is the same. There is no difference. So you can use it safely.

blocks|key|2260739|text|Objects.isNull是用于Java8lambda过滤的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2260740|写起来容易得多，写得更清楚：|2260741|.stream().filter(Objects::isNull)+|code-block|syntax|javascript|2260742|比写：|2260743|.stream().filter(x+->+x+==+null).++|2260744|但是，在if语句中，这两种方法都可以工作。==+null的使用可能更容易阅读，但最终它将归结为一种样式偏好。|2260745|entityMap^0|0|E|0|0|0|0|0|4|2|L|7|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|X|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|Y|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|Z|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|10|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|11|8|@$9|12|A|13|B|C]|$9|14|A|15|B|C]]|D|@]|E|$]]|$1|S|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|T|$]]

<code>Objects.isNull</code> is intended for use within Java 8 lambda filtering. 

It's much easier and clearer to write:

<pre><code>.stream().filter(Objects::isNull) 
</code></pre>

than to write:

<pre><code>.stream().filter(x -&gt; x == null). 
</code></pre>

Within an <code>if</code> statement, however, either will work. The use of <code>== null</code> is probably easier to read but in the end it will boil down to a style preference.

blocks|key|1507877|text|请看资料来源：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1507878|public+static+boolean+isNull(Object+obj)+{
++++return+obj+==+null;
}|code-block|syntax|javascript|1507879|要检查null值，可以使用：|offset|length|style|CODE|1507880|Objects.isNull(myObject)|unordered-list-item|1507881|null+==+myObject+//+avoids+assigning+by+typo|1507882|myObject+==+null+//+risk+of+typo|1507883|Objects.isNull是针对Predicate的这一事实并不妨碍您如上所示地使用它。|1507884|entityMap^0|0|0|3|4|0|0|O|0|0|18|0|0|W|0|0|E|H|9|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Z|8|@$I|10|J|11|K|L]]|9|@]|A|$]]|$1|M|3|N|5|O|7|12|8|@$I|13|J|14|K|L]]|9|@]|A|$]]|$1|P|3|Q|5|O|7|15|8|@$I|16|J|17|K|L]]|9|@]|A|$]]|$1|R|3|S|5|O|7|18|8|@$I|19|J|1A|K|L]]|9|@]|A|$]]|$1|T|3|U|5|6|7|1B|8|@$I|1C|J|1D|K|L]|$I|1E|J|1F|K|L]]|9|@]|A|$]]|$1|V|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]]|W|$]]

Look at the source:

<pre><code>public static boolean isNull(Object obj) {
 return obj == null;
}
</code></pre>

To check for <code>null</code> values, you can use:

<ul>
<li><code>Objects.isNull(myObject)</code></li>
<li><code>null == myObject // avoids assigning by typo</code></li>
<li><code>myObject == null // risk of typo</code></li>
</ul>

The fact that <code>Objects.isNull</code> is meant for <code>Predicate</code>s does not prevent you from using it as above.

blocks|key|1507954|text|在==+if语句中，对于Objects.isNull()，有什么理由/情况应该使用+null吗？|type|blockquote|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|1507955|是的，原因之一是使代码保持简单。在if语句中，+object+==+null是明确的和众所周知的。它不会导致任何不当行为，例如，有一个错误。|unstyled|CODE|1507956|我的理解是，通过省略第二个=，Objects.isNull()将消除意外地将空值赋值给对象的可能性。|1507957|如果有一个if+(object+=+null)+{}+(省略了+=+)，它将不会编译，或者在遇到Boolean对象时会生成警告！实际上，没有理由在Objects.isNull(object)+if语句中使用+over+。下面是两个并排的变体：|1507958|if+(object+==+null)+{
}

if+(Objects.isNull(object))+{
}|code-block|syntax|javascript|1507959|Objects.isNull()应该仅限于谓词吗？|1507960|可以说是的，它仅限于谓词，尽管在任何地方使用Objects.isNull()都没有技术障碍。|1507961|来自public+static+boolean+isNull(Object+obj)方法的javadoc：|1507962|@apeNote此方法存在，用作一个java.util.function.Predicate，过滤器(对象：：isNull)|1507963|因此，如果将该方法用作而不是(谓词)，则实际上使用的表达式比简单的object+==+null更复杂和麻烦。|1507964|下面是一个比较Objects.isNull(object)好处的片段|1507965|List<String>+list+=+Arrays.asList("a",+"b",+null,+"c",+null);

//+As+ready-made+predicate
long+countNullsWithPredicate+=+list.stream().filter(Objects::isNull).count();

//+Lambda
long+countNullsWithLambda+=+list.stream().filter(object+->+object+==+null).count();

//+Reimplement+the+Objects::isNull+predicate
long+countNullsWithAnonymous+=+list.stream().filter(new+Predicate<Object>()+{
++++@Override
++++public+boolean+test(Object+obj)+{
++++++++return+obj+==+null;
++++}
}).count();|1507966|entityMap^0|15|7|0|0|N|O|1A|O|E|0|0|1E|0|0|V|W|1W|2V|6|5|L|W|1|1C|7|21|M|0|0|0|M|G|0|2|14|0|0|B|3|X|E|0|7|M|0|0^^$0|@$1|2|3|4|5|6|7|18|8|@$9|19|A|1A|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|1B|8|@$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]|$9|1G|A|1H|B|I]]|D|@]|E|$]]|$1|J|3|K|5|6|7|1I|8|@$9|1J|A|1K|B|C]]|D|@]|E|$]]|$1|L|3|M|5|H|7|1L|8|@$9|1M|A|1N|B|C]|$9|1O|A|1P|B|C]|$9|1Q|A|1R|B|C]|$9|1S|A|1T|B|I]|$9|1U|A|1V|B|I]|$9|1W|A|1X|B|I]|$9|1Y|A|1Z|B|I]]|D|@]|E|$]]|$1|N|3|O|5|P|7|20|8|@]|D|@]|E|$Q|R]]|$1|S|3|T|5|6|7|21|8|@]|D|@]|E|$]]|$1|U|3|V|5|H|7|22|8|@$9|23|A|24|B|I]]|D|@]|E|$]]|$1|W|3|X|5|H|7|25|8|@$9|26|A|27|B|I]]|D|@]|E|$]]|$1|Y|3|Z|5|6|7|28|8|@]|D|@]|E|$]]|$1|10|3|11|5|H|7|29|8|@$9|2A|A|2B|B|C]|$9|2C|A|2D|B|I]]|D|@]|E|$]]|$1|12|3|13|5|H|7|2E|8|@$9|2F|A|2G|B|I]]|D|@]|E|$]]|$1|14|3|15|5|P|7|2H|8|@]|D|@]|E|$Q|R]]|$1|16|3|-4|5|H|7|2I|8|@]|D|@]|E|$]]]|17|$]]

<blockquote>
 Would there be any reason/circumstance for which I should use object == null over Objects.isNull() in a if statement?
</blockquote>

Yes, one reason is to keep the code simple. Within if statement <code>object == null</code> is clear and well known. It can not lead to any misbehavior if for example there is a typo.

<blockquote>
 My understanding is that Objects.isNull() would remove the chance of accidentally assigning a null value to object by omitting the second =.
</blockquote>

If there is an <code>if (object = null) {}</code> with omitted <code>=</code> it will not compile or it will generate warning in case of <code>Boolean</code> object! Actually there is no reason to use <code>Objects.isNull(object)</code> over <code>object == null</code> within if statement. Here are the two variants side by side:

<pre><code>if (object == null) {
}

if (Objects.isNull(object)) {
}
</code></pre>

<blockquote>
 Should Objects.isNull() be confined to Predicates exclusively?
</blockquote>

It could be said yes, it is confined to Predicates exclusively, although there is no technical hurdle to use the <code>Objects.isNull()</code> everywhere.

From the <code>public static boolean isNull(Object obj)</code> method's javadoc: 

<blockquote>
 @apiNoteThis method exists to be used as a java.util.function.Predicate, filter(Objects::isNull)
</blockquote>

So if you use the method as not a predicate you are actually using a more complex and cumbersome expression compared to the simple <code>object == null</code>.

Here is a snippet to compare the benefit of <code>Objects.isNull(object)</code>

<pre><code>List&lt;String&gt; list = Arrays.asList("a", "b", null, "c", null);

// As ready-made predicate
long countNullsWithPredicate = list.stream().filter(Objects::isNull).count();

// Lambda
long countNullsWithLambda = list.stream().filter(object -&gt; object == null).count();

// Reimplement the Objects::isNull predicate
long countNullsWithAnonymous = list.stream().filter(new Predicate&lt;Object&gt;() {
 @Override
 public boolean test(Object obj) {
 return obj == null;
 }
}).count();
</code></pre>

blocks|key|1158605|text|在语义上没有区别，但为了可读性，我更喜欢下面的内容，而不是whatever+==+null|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1158606|import+static+java.util.Objects.isNull;

//+Other+stuff...

if(isNull(whatever))+{+

}|code-block|syntax|javascript|1158607|entityMap^0|T|G|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Semantically there is no difference but for readability I prefer the following over <code>whatever == null</code>:

<pre><code>import static java.util.Objects.isNull;

// Other stuff...

if(isNull(whatever)) { 

}
</code></pre>

As you know, <a href="https://docs.oracle.com/javase/8/docs/api/java/util/Objects.html" rel="noreferrer"><code>java.util.Objects</code></a> is 

<blockquote>
 This class consists of static utility methods for operating on objects.
</blockquote>

One of such methods is <code>Objects.isNull()</code>.

My understanding is that <code>Objects.isNull()</code> would remove the chance of accidentally assigning a null value to object by omitting the second <code>=</code>.

However, the API Note states:

<blockquote>
 This method exists to be used as a Predicate, filter(Objects::isNull)
</blockquote>

Would there be any reason/circumstance for which I should use <code>object == null</code> over <code>Objects.isNull()</code> in an if statement?

Should <code>Objects.isNull()</code> be confined to Predicates exclusively?

java.util.Objects.isNull vs object == null

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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如你所知，是该类由用于操作对象的静态实用程序方法组成。其中一种方法是Objects.isNull()。我的理解是，Objects.isNull()将通过省略第二个=来消除意外将空值分配给对象的可能性。然而，API说明指出：此方法存在，用作谓词过滤器(Object：：isNull)在object == null if语句中，是否存在使用 over 的任何理由/情况？Objects.isNull()是

问java.util.Objects.isNull与对象==空
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