ClassCastException when converting from String to Object.. why?

I am just playing with MessageFormat but when I try to pass a String to MessageFormat format method it compiles fine but then I get a runtime classcast exception. Here is the code.

MessageFormat format = new MessageFormat(""); Object obj = Integer.toHexString(10); format.format(obj);

Now the runtime exception I get is as follows.

Exception in thread "main" java.lang.开发者_高级运维ClassCastException: java.lang.String cannot be cast to [Ljava.lang.Object; at java.text.MessageFormat.format(Unknown Source) at java.text.Format.format(Unknown Source) at JavaCore2.Codepoint.main(Codepoint.java:21)

MessageFormat.format() takes an argument of type Object[] (an Object array), whereas you are passing in a single Object.

You will have to create an array out of your Integer:

MessageFormat format = new MessageFormat("{0}");
Object[] args = { Integer.toHexString(10) };

String result = format.format(args);