blocks|key|155734|text|someList.toString()不是序列化数据的适当方式，而且会给您带来麻烦。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|155735|由于您需要将其作为字符串存储在cookie中，因此请使用JSON或XML。google-gson可能是一个很好的库：|155736|ArrayList+str+=+(ArrayList)+retrieveList.get(1);
String+content+=+new+Gson().toJson(str);
makeCookie("userCredentialsCookie",+content,+httpServletResponce);
//...
ArrayList+userCredntialsList+=+new+Gson().fromJson(cookie.getValue(),+ArrayList.class);|code-block|syntax|javascript|155737|entityMap|0|LINK|mutability|MUTABLE|url|http://code.google.com/p/google-gson/^0|0|J|0|11|B|0|0|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|@$9|Y|A|Z|1|10]]|E|$]]|$1|H|3|I|5|J|7|11|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

<code>someList.toString()</code> is not a proper way of serializing your data and will get you into trouble.

Since you need to store it as a String in a cookie, use JSON or XML. <a href="http://code.google.com/p/google-gson/" rel="nofollow">google-gson</a> might be a good lib for you:

<pre><code>ArrayList str = (ArrayList) retrieveList.get(1);
String content = new Gson().toJson(str);
makeCookie("userCredentialsCookie", content, httpServletResponce);
//...
ArrayList userCredntialsList = new Gson().fromJson(cookie.getValue(), ArrayList.class);
</code></pre>

blocks|key|155784|text|您不能直接将String转换为ArrayList，而是需要创建一个ArrayList对象来保存String值。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|155785|您需要更改以下代码的一部分：|155786|ArrayList+userCredntialsList+=+(ArrayList)value;++//Need+String+to+ArrayList+
session.setAttribute(attributeName,+userCredntialsList);|code-block|syntax|javascript|155787|至：|155788|ArrayList<String>+userCredentialsList+=+(+ArrayList<Strnig>+)+session.getAttribute(+attributeName+);
if+(+userCredentialsList+==+null+)+{
++++userCredentialsList+=+new+ArrayList<String>(+10+);
++++session.setAttribute(attributeName,+userCredentialsList);
}

userCredentialsList.add(+value+);|155789|entityMap^0|6|6|F|9|X|9|1B|6|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|11|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|12|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|13|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|14|8|@]|D|@]|E|$K|L]]|$1|Q|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|R|$]]

You can't directly cast a <code>String</code> to <code>ArrayList</code> instead you need to create an <code>ArrayList</code> object to hold <code>String</code> values. 

You need to change part of your code below: 

<pre><code>ArrayList userCredntialsList = (ArrayList)value; //Need String to ArrayList 
session.setAttribute(attributeName, userCredntialsList);
</code></pre>

to: 

<pre><code>ArrayList&lt;String&gt; userCredentialsList = ( ArrayList&lt;Strnig&gt; ) session.getAttribute( attributeName );
if ( userCredentialsList == null ) {
 userCredentialsList = new ArrayList&lt;String&gt;( 10 );
 session.setAttribute(attributeName, userCredentialsList);
}

userCredentialsList.add( value );
</code></pre>

blocks|key|155848|text|只要它是String对象的ArrayList，您就应该能够编写一个小方法，该方法可以解析单个String以重新创建列表。ArrayList的toString将如下所示：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|155849|"[foo,+bar,+baz]"|code-block|syntax|javascript|155850|因此，如果该字符串在变量value中，则可以执行以下操作：|155851|String+debracketed+=+value.replace("[",+"").replace("]",+"");+//+now+be+"foo,+bar,+baz"
String+trimmed+=+debracketed.replaceAll("\\s%2B",+"");+//+now+is+"foo,bar,baz"
ArrayList<String>+list+=+new+ArrayList<String>(Arrays.asList(trimmed.split(",")));+//+now+have+an+ArrayList+containing+"foo",+"bar"+and+"baz"|155852|请注意，这是未经测试的代码。|155853|此外，如果您的原始ArrayList不是String的列表，而是一个ArrayList<MyDomainObject>，那么这种方法将不起作用。为此，您应该找到如何正确序列化/反序列化您的对象-+toString通常不是一个有效的方法。如果是这样的话，更新这个问题是值得的。|155854|entityMap^0|4|6|D|9|1A|6|1O|9|1Y|8|0|0|C|5|0|0|0|9|9|K|6|Y|P|2Q|8|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|19|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1A|8|@]|D|@]|E|$]]|$1|Q|3|R|5|6|7|1B|8|@$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]|$9|1G|A|1H|B|C]|$9|1I|A|1J|B|C]]|D|@]|E|$]]|$1|S|3|-4|5|6|7|1K|8|@]|D|@]|E|$]]]|T|$]]

As long as it's an <code>ArrayList</code> of <code>String</code> objects you should be able to write a small method which can parse the single <code>String</code> to re-create the list. The <code>toString</code> of an <code>ArrayList</code> will look something like this:

<pre><code>"[foo, bar, baz]"
</code></pre>

So if that String is in the variable <code>value</code>, you could do something like this:

<pre><code>String debracketed = value.replace("[", "").replace("]", ""); // now be "foo, bar, baz"
String trimmed = debracketed.replaceAll("\\s+", ""); // now is "foo,bar,baz"
ArrayList&lt;String&gt; list = new ArrayList&lt;String&gt;(Arrays.asList(trimmed.split(","))); // now have an ArrayList containing "foo", "bar" and "baz"
</code></pre>

Note, this is untested code.

Also, if it is not the case that your original <code>ArrayList</code> is a list of <code>String</code>s, and is instead say, an <code>ArrayList&lt;MyDomainObject&gt;</code>, this approach will not work. For that your should instead find how to serialise/deserialise your objects correctly - <code>toString</code> is generally not a valid approach for this. It would be worth updating the question if that is the case.

I have an ArrayList, Whom i convert to String like

<pre><code>ArrayList str = (ArrayList) retrieveList.get(1);
...

makeCookie("userCredentialsCookie", str.toString(), httpServletResponce);
....

private void makeCookie(String name, String value, HttpServletResponse response) {

 Cookie cookie = new Cookie(name, value);
 cookie.setPath("/");
 response.addCookie(cookie);

} //end of makeCookie()
</code></pre>

Now when i retrieve cookie value, i get String, but i again want to convert it into ArrayList like

<pre><code>private void addCookieValueToSession(HttpSession session, Cookie cookie, String attributeName) { 
 if (attributeName.equalsIgnoreCase("getusercredentials")) {

 String value = cookie.getValue();
 ArrayList userCredntialsList = (ArrayList)value; //Need String to ArrayList 
 session.setAttribute(attributeName, userCredntialsList);
 return;
 }

 String value = cookie.getValue();
 session.setAttribute(attributeName, value);

} //end of addCookieValueToSession
</code></pre>

How can i again convert it to ArrayList? 
Thank you.

How to convert String representation of ArrayList to ArrayList

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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我有一个ArrayList，我将其转换为字符串，如ArrayList str = (ArrayList) retrieveList.get(1);...makeCookie("userCredentialsCookie", str.toString(), httpServletResponce);....private...

问如何将ArrayList的字符串表示形式转换为ArrayList
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问如何将ArrayList的字符串表示形式转换为ArrayListEN