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I'm doing the following

 String s = caseInsensitiveMap.get("buyerCode");

and I'm getting the error

java.lang.ClassCastException: [Ljava.lang.String; incompatible with java.lang.String

I just cannot figure out what I'm doing wrong. Googling the answer seems to point towards needing to use a String[] somewhere, but I have no idea where.

More relevent information:

caseInsensitiveMap : Map caseInsensitiveMap - com.msw.commerce.me.commands.MSWOrgCmdImpl.setRequestProperties(TypedProperty)

.get() : String java.util.Map.get(Object key)

I have also attempted to do 

String s = caseInsensitiveMap.get((Object) "buyerCode");

to explicitly cast the string "buyerCode" to it's needed Object type, but I get the same error.

Can someone please tell me what I'm doing wrong? From what I can see, I'm matching all of the types here. .get() takes an Object, and I'm giving it an object. It returns a String, and I'm assigning it to a String.

Edit: more code

public void setRequestProperties(TypedProperty reqProperties)
        throws ECException {
    Map<String, String> reqMap = reqProperties.getMap();
    Map<String, String> caseInsensitiveMap = new TreeMap<String, String>(
            String.CASE_INSENSITIVE_ORDER);
    caseInsensitiveMap.putAll(reqMap);

Here are the docs for TypedProperty

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3  
Show us the relevant code. How is caseInsensitiveMap declared, initialized and populated? – JB Nizet May 3 '16 at 19:00
2  
[Ljava.lang.String means String[], in other words, you are getting an array of Strings, which is not the same as a single String. See also here: stackoverflow.com/questions/3442090/… – Florian Schaetz May 3 '16 at 19:01
    
Your map contains a String[] as the value instead of the String you are expecting. Maps can generally contain any type of object and in your case, you are inserting the wrong type without realizing it. – Mad Physicist May 3 '16 at 19:02
    
Based on the error message, caseInsensitiveMap.get() is returning an array of Strings, not a String. Without your code, it's impossible to analyze further. – Mike Harris May 3 '16 at 19:03
1  
Do you get any warning at the line Map<String, String> reqMap = reqProperties.getMap();? – Eran May 3 '16 at 19:06
up vote 2 down vote accepted

It's almost a certainty that TypedProperty.getMap() is heterogeneous. It's really a map from String keys to Objects, and it's therefore unsafe to assign it to a variable of type Map< String, String >. If you aren't getting a warning at the line

Map<String, String> reqMap = reqProperties.getMap();

it's probably because the warnings about unchecked conversions are disabled in your development environment.

The problem is not the type of the key; the problem is the type of the value you're trying to add to your TreeMap. You can't cast an array of String to a String, so putAll() is going to fail.

Try declaring your TreeMap as

Map<String, Object> reqMap = reqProperties.getMap();
Map<String, Object> caseInsensitiveMap = new TreeMap<String, Object>(
        String.CASE_INSENSITIVE_ORDER);
share|improve this answer
    
You were correct. Whoever wrote the code that set caseInsensitiveMap (as well as myself) did not realize that TypedProperties in no way guarantee <String, String>. – jros May 3 '16 at 19:33

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