blocks|key|1669233|text|Singleton+singleton+=+Singleton.getInstance();|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1669234|才是正确的方法。确保您的getInstance()方法确实是static。|unstyled|offset|length|style|CODE|1669235|由于您的Singleton实现远非安全？？您的对象可以通过反射进行实例化，因此您可能希望基于enum创建一个单例。|1669236|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/427902/java-enum-singleton^0|0|C|D|U|6|0|4|9|1A|4|1A|4|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|V|8|@$G|W|H|X|I|J]|$G|Y|H|Z|I|J]]|9|@]|A|$]]|$1|K|3|L|5|F|7|10|8|@$G|11|H|12|I|J]|$G|13|H|14|I|J]]|9|@$G|15|H|16|1|17]]|A|$]]|$1|M|3|-4|5|F|7|18|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

<pre><code>Singleton singleton = Singleton.getInstance();
</code></pre>

is the correct way. Make sure your <code>getInstance()</code> method is indeed <code>static</code>.

Since your <code>Singleton</code> implementation is far from being safe - your object can be instantiated via reflection, you may want to create a singleton based on <a href="https://stackoverflow.com/questions/427902/java-enum-singleton"><code>enum</code></a>

blocks|key|1669279|text|Singleton+singleton+=+Singleton.getInstance();应该能工作--考虑到您的代码，这个错误没有意义；您确定您报告的是正确的吗？(如果您忘记将getInstance方法静态化，这将是有意义的，因为您已经在上面的代码中这样做了。)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1669280|你给我们的课程代码是正确的。|1669281|最后，一个概念上的注意事项:首先，您不是“创建Singleton类的对象”--这是Singleton的全部要点。)您只是获得了对现有对象的引用。|1669282|entityMap^0|0|1A|2I|B|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|R|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|K|$]]

<code>Singleton singleton = Singleton.getInstance();</code> should work -- that error doesn't make sense, given your code; are you sure you're reporting it correctly? (It would make sense if you had forgotten to make the <code>getInstance</code> method static, which you've done in your code above.)

The code you've given us for the class is correct.

Lastly, one conceptual note: First, you aren't "creating an object of class Singleton" -- that's the whole point of a Singleton. :) You're just getting a reference to the existing object.

blocks|key|119642|text|这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|119643|+Singleton+singleton+=+Singleton.getInstance();|code-block|syntax|javascript|119644|应该行得通。这就是在Java中调用静态方法的方式。getInstance()方法声明为static。您确定您使用的是同一个Singleton类吗？或者您已经在其他包中导入了一个名为“相同”的类。|offset|length|style|CODE|119645|entityMap^0|0|0|P|D|17|6|1P|9|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]|$I|T|J|U|K|L]|$I|V|J|W|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|N|$]]

This one:

<pre><code> Singleton singleton = Singleton.getInstance();
</code></pre>

should work. This is how you call static methods in Java. And the <code>getInstance()</code> method is declared as <code>static</code>. Are you sure you are using the very same <code>Singleton</code> class? Or maybe you have imported a class called the same in some other package.

blocks|key|1669331|text|由于构造函数是私有的，所以使用构造函数创建对象是没有意义的。|type|ordered-list-item|depth|inlineStyleRanges|entityRanges|data|1669332|您应该使用public+static+Singleton+getInstance()，但是实现不是很正确。
if+(instance+==+null)+{
instance+=+new+Singleton();
}
return+instance;|offset|length|style|CODE|1669333|你应该这么做。这确保它在不存在的情况下创建实例，或者只返回现有实例。您的代码也会做同样的事情，但是这增加了可读性。|unstyled|1669334|entityMap^0|0|5|11|1I|N|26|R|2Y|1|30|G|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@$D|O|E|P|F|G]|$D|Q|E|R|F|G]|$D|S|E|T|F|G]|$D|U|E|V|F|G]|$D|W|E|X|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|Y|8|@]|9|@]|A|$]]|$1|K|3|-4|5|J|7|Z|8|@]|9|@]|A|$]]]|L|$]]

<ol>
<li>since the constructor is private, it does not make sense to create an object using the constructor.</li>
<li>you should be using <code>public static Singleton getInstance()</code>, but the implementation is not very correct.

<code>if (instance == null) { 
 instance = new Singleton(); 
} 
return instance;</code></li>
</ol>

This is how you should be doing it. This ensure that it creates the instance if it does not exist, or simply returns the existing instance. Your code would also do the same thing, but this add to the readability.

blocks|key|119707|text|因为我们不希望允许访问多个副本。因此，我们需要手动实例化一个对象，但我们需要保留对该单例的引用，以便后续对访问器方法的调用可以返回单例(而不是创建一个新的)。这就是为什么|type|unstyled|depth|inlineStyleRanges|entityRanges|data|119708|Singleton+singleton+=+Singleton.getInstance();|code-block|syntax|javascript|119709|访问任何singletonObject的正确方法。|119710|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Since we doesn't want to allow more than one copy to be accessed. So We need to manually instantiate an object, but we need to keep a reference to the singleton so that subsequent calls to the accessor method can return the singleton (rather than creating a new one).
Thats why is 

<pre><code>Singleton singleton = Singleton.getInstance();
</code></pre>

Correct way to access any singletonObject.

blocks|key|1669292|text|使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1669293|Singleton+singleton+=+Singleton.getInstance();
//+error+-+non-static+method+cannot+be+referenced+from+a+static+context|code-block|syntax|javascript|1669294|这是从类中获取单例对象的方法。一定还有别的事要做。请张贴更多细节|1669295|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

There is nothing wrong in using 

<pre><code>Singleton singleton = Singleton.getInstance();
// error - non-static method cannot be referenced from a static context
</code></pre>

This is the way to get the singleton object form the class. There must me something else. Please post some more details

blocks|key|1363776|text|仍然可以创建类的多个实例，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1363777|Singleton.getInstance().clone()|code-block|syntax|javascript|1363778|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|$]]

It is still possible to create more than one instance of the class, as follows:

<pre><code>Singleton.getInstance().clone()
</code></pre>

blocks|key|1364240|text|由于getInstance()方法也是“静态”和实例字段，yo可以使用Singleton.getInstance()；而无需创建类的新实例。硫是单酮的靶子|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1364241|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

since getInstance() method is "static" and instance field too, yo can use Singleton.getInstance(); Without creating new exeple of class. Thihs is the poit of singletone

Edit: Answered - error was method wasn't static

I'm used the <a href="http://en.wikipedia.org/wiki/Singleton_pattern" rel="noreferrer">Singleton Design Pattern</a>

<pre><code> public class Singleton {
 private static final Singleton INSTANCE = new Singleton();

 // Private constructor prevents instantiation from other classes
 private Singleton() {}

 public static Singleton getInstance() {
 return INSTANCE;
 }
 }
</code></pre>

My question is how do I create an object of class Singleton in another class?

I've tried:

<pre><code>Singleton singleton = new Singleton(); 
// error - constructor is private
Singleton singleton = Singleton.getInstance();
// error - non-static method cannot be referenced from a static context
</code></pre>

What is the correct code?

Thanks,
Spencer

Java Singleton Pattern

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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编辑:答案-错误是方法不是静态的我用的是 public class Singleton {   private static final Singleton INSTANCE = new Singleton();   // Private constructor prevents instantiation from other classes   private Singleton() {}  

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