[java.lang.String; cannot be cast to java.lang.String

Question

I'm obtaining a Vector from a product's API.

Vector<?> dataVector = dataAPI.getReturnVector();

The vector is expected to contain Strings as value. I'm able to print the size of the vector as 2. But for some reason I'm not able to iterate and print the values.

I tried

Iterator<?> iter = dataVector.iterator();

while( iter.hasNext()) {
    System.out.println(iter.next());
}

I always end up getting a

[java.lang.String; cannot be cast to java.lang.String

I used

iter.next().getClass().getName() 

and it turned out to be java.lang.String only.

I googled a bit and found a similar problem at http://prideafrica.blogspot.com/2007/01/javalangclasscastexception.html

I tried to set the generics as String[], but ended up with the same error.

If the vector contains java.lang.String, why do I get this cast exception? How can I print the actual values?

Kindly provide your suggestions.

Answer 1

So the API is not returning a Vector of Strings but a Vector of String[].

You should be able to iterate through the vector and then, for each element, loop through the array.

Iterator<String[]> iter = dataVector.iterator();

while( iter.hasNext()) {
    String[] array = iter.next();
    for(int i=0; i < array.length; i++)
    {
       System.out.println(i + ": " + array[i]);
    }
}

Answer 2

Try compare their classLoaders. If they are different, then this Exception occur.

StringClass1.getClassLoader()==StringClass2.getClassLoader();

Answer 3

No need to use an iterator. You could just use the elementAt(index) method of Vectors to print the values. Use a For loop to get the indices of the Vector.

Example:

Vector<?> dataVector = dataAPI.getReturnVector();
for(int i = 0; i < dataVector.size(); i++) {
    System.out.println(dataVector.elementAt(i));
}

If you are getting a strange answer (of numbers and letters), you getting a String[] object. That means you will have use the built-in method of Arrays to print the String[] array. See the comments below.