blocks|key|774316|text|如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|774317|final+int+myVariable+=+1;

myButton.addActionListener(new+ActionListener()+{
++++public+void+actionPerformed(ActionEvent+e)+{
++++++++//+Now+you+can+access+it+alright.
++++}
});|code-block|syntax|javascript|774318|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|$]]

Like this:

<pre><code>final int myVariable = 1;

myButton.addActionListener(new ActionListener() {
 public void actionPerformed(ActionEvent e) {
 // Now you can access it alright.
 }
});
</code></pre>

blocks|key|774371|text|是的，通过添加一个返回'this‘的初始化器方法，并立即调用该方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|774372|int+myVariable+=+1;

myButton.addActionListener(new+ActionListener()+{
++++private+int+anonVar;
++++public+void+actionPerformed(ActionEvent+e)+{
++++++++//+How+would+one+access+myVariable+here?
++++++++//+It's+now+here:
++++++++System.out.println("Initialized+with+value:+"+%2B+anonVar);
++++}
++++private+ActionListener+init(int+var){
++++++++anonVar+=+var;
++++++++return+this;
++++}
}.init(myVariable)++);|code-block|syntax|javascript|774373|不需要'final‘声明。|774374|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|$]]

Yes, by adding an initializer method that returns 'this', and immediately calling that method:

<pre><code>int myVariable = 1;

myButton.addActionListener(new ActionListener() {
 private int anonVar;
 public void actionPerformed(ActionEvent e) {
 // How would one access myVariable here?
 // It's now here:
 System.out.println("Initialized with value: " + anonVar);
 }
 private ActionListener init(int var){
 anonVar = var;
 return this;
 }
}.init(myVariable) );
</code></pre>

No 'final' declaration needed.

blocks|key|774394|text|如http://www.coderanch.com/t/567294/java/java/declare-constructor-anonymous-class所示，您可以添加一个实例初始化器。它是一个没有名称的块，并且首先被执行(就像构造函数一样)。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|774395|看起来在Why+java+Instance+initializers?上也讨论了它们，How+is+an+instance+initializer+different+from+a+constructor?讨论了与构造函数的区别。|774396|entityMap|0|LINK|mutability|MUTABLE|url|http://www.coderanch.com/t/567294/java/java/declare-constructor-anonymous-class|1|https://stackoverflow.com/questions/6763550/why-java-instance-initializers|2|https://stackoverflow.com/questions/1355810/how-is-an-instance-initializer-different-from-a-constructor^0|1|27|0|0|4|V|1|17|1O|2|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@$A|S|B|T|1|U]]|C|$]]|$1|D|3|E|5|6|7|V|8|@]|9|@$A|W|B|X|1|Y]|$A|Z|B|10|1|11]]|C|$]]|$1|F|3|-4|5|6|7|12|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]|P|$5|I|J|K|C|$L|Q]]]]

As shown at <a href="http://www.coderanch.com/t/567294/java/java/declare-constructor-anonymous-class" rel="nofollow noreferrer">http://www.coderanch.com/t/567294/java/java/declare-constructor-anonymous-class</a> you can add an instance initializer. It's a block that doesn't have a name and gets executed first (just like a constructor).

Looks like they're also discussed at <a href="https://stackoverflow.com/questions/6763550/why-java-instance-initializers">Why java Instance initializers?</a> and <a href="https://stackoverflow.com/questions/1355810/how-is-an-instance-initializer-different-from-a-constructor">How is an instance initializer different from a constructor?</a> discusses differences from constructors.

blocks|key|774428|text|其他人已经回答说匿名类只能访问final变量。但是他们留下了一个悬而未决的问题，如何保持原始变量不是最终变量。Adam+Mlodzinski给出了一个解决方案，但它相当臃肿。对于这个问题，有一个更简单的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|774429|如果您不希望myVariable是最终的，那么您必须将它包装在一个新的作用域中，如果它是最终的，那么它并不重要。|style|CODE|774430|int+myVariable+=+1;

{
++++final+int+anonVar+=+myVariable;

++++myButton.addActionListener(new+ActionListener()+{
++++++++public+void+actionPerformed(ActionEvent+e)+{
++++++++++++//+How+would+one+access+myVariable+here?
++++++++++++//+Use+anonVar+instead+of+myVariable
++++++++}
++++});
}|code-block|syntax|javascript|774431|Adam+Mlodzinski在他的答案中没有做任何其他事情，只是用了更多的代码。|774432|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/12206542/402322^0|1J|F|0|0|6|A|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|6|7|10|8|@$A|11|B|12|F|G]]|9|@]|C|$]]|$1|H|3|I|5|J|7|13|8|@]|9|@]|C|$K|L]]|$1|M|3|N|5|6|7|14|8|@]|9|@]|C|$]]|$1|O|3|-4|5|6|7|15|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]]]

Other people have already answered that anonymous classes can access only final variables. But they leave the question open how to keep the original variable non-final. <a href="https://stackoverflow.com/a/12206542/402322">Adam Mlodzinski</a> gave a solution but is is pretty bloated. There is a much simpler solution for the problem:

If you do not want <code>myVariable</code> to be final you have to wrap it in a new scope where it does not matter, if it is final.

<pre><code>int myVariable = 1;

{
 final int anonVar = myVariable;

 myButton.addActionListener(new ActionListener() {
 public void actionPerformed(ActionEvent e) {
 // How would one access myVariable here?
 // Use anonVar instead of myVariable
 }
 });
}
</code></pre>

Adam Mlodzinski does not do anything else in his answer but with much more code.

blocks|key|774519|text|将一些值放入外部变量(不属于匿名类)的一个简单方法是如何操作！|type|unstyled|depth|inlineStyleRanges|entityRanges|data|774520|同样，如果你想获取外部变量的值，你可以创建一个返回你想要的东西的方法！|774521|public+class+Example{

++++private+TypeParameter+parameter;

++++private+void+setMethod(TypeParameter+parameter){

++++++++this.parameter+=+parameter;

++++}

++++//...
++++//into+the+anonymus+class
++++new+AnonymusClass(){

++++++++final+TypeParameter+parameterFinal+=+something;
++++++++//you+can+call+setMethod(TypeParameter+parameter)+here+and+pass+the
++++++++//parameterFinal
++++++++setMethod(parameterFinal);+

++++++++//now+the+variable+out+the+class+anonymus+has+the+value+of
++++++++//of+parameterFinal

++++});

+}|code-block|syntax|javascript|774522|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|$]]

A simple way for put some value into a external variable(doesn't belong for anonymus class)
is how folow!
 
In the same way if you want get the value of a external variable you can create a method that return what you want! 


<pre><code>public class Example{

 private TypeParameter parameter;

 private void setMethod(TypeParameter parameter){

 this.parameter = parameter;

 }

 //...
 //into the anonymus class
 new AnonymusClass(){

 final TypeParameter parameterFinal = something;
 //you can call setMethod(TypeParameter parameter) here and pass the
 //parameterFinal
 setMethod(parameterFinal); 

 //now the variable out the class anonymus has the value of
 //of parameterFinal

 });

 }
</code></pre>

blocks|key|989893|text|我认为匿名类基本上就像lambdas，但语法更差……事实证明这是真的，但语法更糟糕，会导致(应该是)局部变量溢出到包含类中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|989894|您可以通过将最终变量设置为父类的字段来访问这些变量。|989895|例如|989896|接口：|989897|public+interface+TextProcessor
{
++++public+String+Process(String+text);
}|code-block|syntax|javascript|989898|类：|989899|private+String+_key;

public+String+toJson()
{
++++TextProcessor+textProcessor+=+new+TextProcessor()+{
++++++++@Override
++++++++public+String+Process(String+text)
++++++++{
++++++++++++return+_key+%2B+":"+%2B+text;
++++++++}
++++};

++++JSONTypeProcessor+typeProcessor+=+new+JSONTypeProcessor(textProcessor);

++++foreach(String+key+:+keys)
++++{
++++++++_key+=+key;

++++++++typeProcessor.doStuffThatUsesLambda();
++++}|989900|我不知道他们是否在java+8中解决了这个问题(我被困在EE世界中，还没有得到8)，但在C#中它会是这样的：|989901|++++public+string+ToJson()
++++{
++++++++string+key+=+null;
++++++++var+typeProcessor+=+new+JSONTypeProcessor(text+=>+key+%2B+":"+%2B+text);

++++++++foreach+(var+theKey+in+keys)
++++++++{
++++++++++++key+=+theKey;

++++++++++++typeProcessor.doStuffThatUsesLambda();
++++++++}
++++}|989902|在c#中你也不需要单独的接口……我怀念它！我发现自己在java中做了更糟糕的设计，并且更多地重复自己，因为你必须在java中添加大量的代码%2B复杂性来重用某些东西，而不仅仅是复制和粘贴很多时间。|989903|entityMap^0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|10|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|11|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|12|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|13|8|@]|9|@]|A|$]]|$1|O|3|P|5|J|7|14|8|@]|9|@]|A|$K|L]]|$1|Q|3|R|5|6|7|15|8|@]|9|@]|A|$]]|$1|S|3|T|5|J|7|16|8|@]|9|@]|A|$K|L]]|$1|U|3|V|5|6|7|17|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|X|$]]

I thought anonymous classes were basically like lambdas but with worse syntax... this turns out to be true but the syntax is even worse and causes (what should be) local variables to bleed out into the containing class.

You can access none final variables by making them into fields of the parent class.

Eg

Interface:

<pre><code>public interface TextProcessor
{
 public String Process(String text);
}
</code></pre>

class:

<pre><code>private String _key;

public String toJson()
{
 TextProcessor textProcessor = new TextProcessor() {
 @Override
 public String Process(String text)
 {
 return _key + ":" + text;
 }
 };

 JSONTypeProcessor typeProcessor = new JSONTypeProcessor(textProcessor);

 foreach(String key : keys)
 {
 _key = key;

 typeProcessor.doStuffThatUsesLambda();
 }
</code></pre>

I dont know if they've sorted this out in java 8 (I'm stuck in EE world and not got 8 yet) but in C# it would look like this:

<pre><code> public string ToJson()
 {
 string key = null;
 var typeProcessor = new JSONTypeProcessor(text =&gt; key + ":" + text);

 foreach (var theKey in keys)
 {
 key = theKey;

 typeProcessor.doStuffThatUsesLambda();
 }
 }
</code></pre>

You dont need a seperate interface in c# either... I miss it! I find myself making worse designs in java and repeating myself more because the amount of code + complexity you have to add in java to reuse something is worse than just copy and pasting a lot of the time.

blocks|key|774672|text|这将会产生魔力|type|unstyled|depth|inlineStyleRanges|entityRanges|data|774673|int+myVariable+=+1;

myButton.addActionListener(new+ActionListener()+{

++++int+myVariable;

++++public+void+actionPerformed(ActionEvent+e)+{
++++++++//+myVariable+...
++++}

++++public+ActionListener+setParams(int+myVariable)+{

++++++++this.myVariable+=+myVariable;

++++++++return+this;
++++}
}.setParams(myVariable));|code-block|syntax|javascript|774674|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|$]]

This will do the magic

<pre><code>int myVariable = 1;

myButton.addActionListener(new ActionListener() {

 int myVariable;

 public void actionPerformed(ActionEvent e) {
 // myVariable ...
 }

 public ActionListener setParams(int myVariable) {

 this.myVariable = myVariable;

 return this;
 }
}.setParams(myVariable));
</code></pre>

blocks|key|990077|text|您可以使用plain+lambdas+("lambda表达式可以捕获变量“)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|990078|int+myVariable+=+1;
ActionListener+al+=+ae->System.out.println(myVariable);
myButton.addActionListener(+al+);|code-block|syntax|javascript|990079|或者甚至是一个函数|990080|Function<Integer,ActionListener>+printInt+=+
++++intvar+->+ae+->+System.out.println(intvar);

int+myVariable+=+1;
myButton.addActionListener(+printInt.apply(myVariable)+);|990081|使用Function是重构装饰器和适配器的好方法，see+here|990082|我刚刚开始学习lambdas，所以如果你发现了一个错误，请随时写下评论。|990083|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html#accessing-local-variables|1|http://techno.emanueleziglioli.it/2017/03/using-java-8s-function-to-refactor.html^0|5|D|0|0|0|0|0|P|8|1|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]]|C|$]]|$1|D|3|E|5|F|7|14|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|15|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|16|8|@]|9|@]|C|$G|H]]|$1|M|3|N|5|6|7|17|8|@]|9|@$A|18|B|19|1|1A]]|C|$]]|$1|O|3|P|5|6|7|1B|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|1C|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]|Y|$5|T|U|V|C|$W|Z]]]]

You can use <a href="https://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html#accessing-local-variables" rel="nofollow noreferrer">plain lambdas</a> ("lambda expressions can capture variables")

<pre><code>int myVariable = 1;
ActionListener al = ae-&gt;System.out.println(myVariable);
myButton.addActionListener( al );
</code></pre>

or even a Function

<pre><code>Function&lt;Integer,ActionListener&gt; printInt = 
 intvar -&gt; ae -&gt; System.out.println(intvar);

int myVariable = 1;
myButton.addActionListener( printInt.apply(myVariable) );
</code></pre>

Using Function is a great way to refactor Decorators and Adapters, <a href="http://techno.emanueleziglioli.it/2017/03/using-java-8s-function-to-refactor.html" rel="nofollow noreferrer">see here</a>

I've just started learning about lambdas, so if you spot a mistake, feel free to write a comment.

blocks|key|775079|text|如果"myVariable“是一个字段，您可以使用限定的this：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|775080|public+class+Foo+{
++++int+myVariable+=+1;

++++new+ActionListener()+{
++++++++public+void+actionPerformed(ActionEvent+e)+{
++++++++++++Foo.this.myVariable+=+8;
++++++++}
++++});
}|code-block|syntax|javascript|775081|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|$]]

If &quot;myVariable&quot; is a field, you can use a qualified this:
<pre><code>public class Foo {
 int myVariable = 1;

 new ActionListener() {
 public void actionPerformed(ActionEvent e) {
 Foo.this.myVariable = 8;
 }
 });
}
</code></pre>

Is it possible to pass parameters, or access external parameters to an anonymous class? For example:

<pre><code>int myVariable = 1;

myButton.addActionListener(new ActionListener() {
 public void actionPerformed(ActionEvent e) {
 // How would one access myVariable here?
 }
});
</code></pre>

Is there any way for the listener to access myVariable or be passed myVariable without creating the listener as an actual named class?

How to pass parameters to anonymous class?

可以向匿名类传递参数或访问外部参数吗？例如：int myVariable = 1;myButton.addActionListener(new ActionListener() {    public void actionPerformed(ActionEvent e) {        // How would o...

问如何将参数传递给匿名类？
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