blocks|key|231860|text|问题是int和long是原语。不能将null传递给原始值。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|231861|您当然可以在方法签名中使用包装类Integer和Long，而不是long和int。|231862|entityMap^0|3|3|7|4|I|4|0|G|7|O|4|W|4|11|3|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|I|$]]

The problem is that <code>int</code> and <code>long</code> are primitives. You can't pass <code>null</code> to a primitive value.

You can certainly use the wrapper classes <code>Integer</code> and <code>Long</code> instead of <code>long</code> and <code>int</code> in your method signature.

blocks|key|226783|text|你不能这么做。在Java中，原始类型不能为null。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|226784|如果想要传递null，则必须将方法签名更改为|226785|public+void+iTakeLong(Long+id);
public+void+iTakeInt(Integer+id);|code-block|syntax|javascript|226786|entityMap^0|L|4|0|6|4|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|U|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

You cannot do that. Primitive types can't be <code>null</code> in Java.

If you want to pass <code>null</code> you have to change your method signature to

<pre><code>public void iTakeLong(Long id);
public void iTakeInt(Integer id);
</code></pre>

blocks|key|226793|text|你不能--没有这样的价值。但是，如果您可以更改方法签名，则可以使其采用引用类型。Java为每个原语类提供了一个不可变的“包装器”类：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|226794|class+TestClass+{
++public+void+iTakeLong(Long+id);
++public+void+iTakeInt(Integer+id);
}|code-block|syntax|javascript|226795|现在，您可以将空引用或引用传递给包装器类型的实例。自动装箱将允许您编写：|226796|iTakeInt(5);|226797|在该方法中，您可以编写：|226798|if+(id+!=+null)+{
++++doSomethingWith(id.intValue());
}|226799|或者使用自动拆箱：|226800|if+(id+!=+null)+{
++++doSomethingWith(id);+//+Equivalent+to+the+code+above
}|226801|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Y|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

You can't - there's no such value. If you can change the method signature, you can make it take a reference type instead though. Java provides an immutable "wrapper" class for each primitive class:

<pre><code>class TestClass {
 public void iTakeLong(Long id);
 public void iTakeInt(Integer id);
}
</code></pre>

Now you can pass a null reference or a reference to an instance of the wrapper type. Autoboxing will allow you to write:

<pre><code>iTakeInt(5);
</code></pre>

Within the method, you can write:

<pre><code>if (id != null) {
 doSomethingWith(id.intValue());
}
</code></pre>

or use automatic unboxing:

<pre><code>if (id != null) {
 doSomethingWith(id); // Equivalent to the code above
}
</code></pre>

blocks|key|231897|text|使用包装器类：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|231898|+TestClass{
++++public+void+iTakeLong(Long+id);
++++public+void+iTakeInt(Integer+id);
++++public+void+iTakeLong(long+id);
++++public+void+iTakeInt(int+id);
+}|code-block|syntax|javascript|231899|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Use the Wrapper classes:

<pre><code> TestClass{
 public void iTakeLong(Long id);
 public void iTakeInt(Integer id);
 public void iTakeLong(long id);
 public void iTakeInt(int id);
 }
</code></pre>

blocks|key|3101306|text|您可以将null强制转换为非原语包装器类，它将进行编译。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3101307|TestClass+testClass+=+new+TestClass();
testClass.iTakeLong(+(Long)null);+//+Compiles
testClass.iTakeInt(+(Integer)null);+++//+Compiles|code-block|syntax|javascript|3101308|但是，这将在执行时抛出NullPointerException。没有太多帮助，但知道您可以传递与将原语作为参数的方法等效的包装器是很有用的。|offset|length|style|CODE|3101309|entityMap^0|0|0|B|K|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

You can cast null to the non-primitive wrapper class, which will compile.

<pre><code>TestClass testClass = new TestClass();
testClass.iTakeLong( (Long)null); // Compiles
testClass.iTakeInt( (Integer)null); // Compiles
</code></pre>

But, this will throw a <code>NullPointerException</code> when executed. Not much help, but it is useful to know that you can pass the wrapper equivalent to a method that takes a primitive as an argument.

blocks|key|231929|text|根据您有多少这样的方法，以及有多少调用，您还有另一种选择。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|231930|您可以编写包装器方法(注意，不是类型包装器(int+=>+Integer)，而是包装您的类型的方法)，而不是在代码库中分发空检查：|231931|public+void+iTakeLong(Long+val)+{
++++if+(val+==+null)+{+
++++++++//+Do+whatever+is+appropriate+here...+throwing+an+exception+would+work
++++}+else+{
++++++++iTakeLong(val.longValue());
++++}
}|code-block|syntax|javascript|231932|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Depending on how many such methods you have, and how many calls, you have another choice.

Instead of distributing null checks throughout your codebase, you can write wrapper methods (N.B., not the type wrappers (int => Integer), but methods which wrap yours):

<pre><code>public void iTakeLong(Long val) {
 if (val == null) { 
 // Do whatever is appropriate here... throwing an exception would work
 } else {
 iTakeLong(val.longValue());
 }
}
</code></pre>

blocks|key|3101335|text|如下所示，将值类型转换为Long将使编译错误消失，但最终将以NullPointerException结束。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3101336|testClass.iTakeLong((Long)null)|code-block|syntax|javascript|3101337|一种解决方案是使用类型Long而不是原语long。|3101338|public+void+iTakeLong(Long+param)+{+}|3101339|另一种解决方案是使用org.apache.commons.lang3.math.NumberUtils|3101340|testClass.iTakeLong(NumberUtils.toLong(null))|3101341|entityMap^0|C|4|U|K|0|0|B|4|K|4|0|0|A|15|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|H|7|19|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|1A|8|@]|D|@]|E|$]]]|T|$]]

Typecasting the value to <code>Long</code> as below will make the compilation error to disappear but eventually will end up in <code>NullPointerException</code>.

<pre><code>testClass.iTakeLong((Long)null)
</code></pre>

One solution is to use type <code>Long</code> instead of primitive <code>long</code>. 

<pre><code>public void iTakeLong(Long param) { }
</code></pre>

Other solution is to use the <code>org.apache.commons.lang3.math.NumberUtils</code> 

<pre><code>testClass.iTakeLong(NumberUtils.toLong(null))
</code></pre>

Could be dumb question, but how can I pass <code>null</code> to method which takes <code>long</code> or <code>int</code>?

Example:

<pre><code>TestClass{
 public void iTakeLong(long id);
 public void iTakeInt(int id);
}
</code></pre>

now how can i pass null to both methos:

<pre><code>TestClass testClass = new TestClass();
testClass.iTakeLong(null); // Compilation error : expected long, got null
testClass.iTakeInt(null); // Compilation error : expected int, got null
</code></pre>

Thoughts, suggestions?

How to pass null to method that expects long or int?

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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这可能是一个愚蠢的问题，但是我如何将null传递给接受long或int的方法示例：TestClass{  public void iTakeLong(long id);  public void iTakeInt(int id);}现在，我如何将null传递给这两个方法：TestClass testClass = ne...

问如何将null传递给需要long或int的方法？
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问如何将null传递给需要long或int的方法？EN