Simple assignment compiler error

Question

Hello,
I'm trying to compile the following statement:
// this is of type FileServer
// v is of type Viewer, which might or might not implement LoggerClient
Object caller = ((v instanceof LoggerClient) ? ((LoggerClient)v) : this);However, compiler gives me
c:\projects\FileServer.java:39: incompatible types
found : FileServer
required: LoggerClient
Why?
Thank you for your help!
Elana

Answer 1

I think you are having a problem of operator Precedence.
The problem is that ?: operator is one of the last in the list.
In your line of code:
Object caller = ((v instanceof LoggerClient) ? ((LoggerClient)v) : this);
happens the following order:
1 - (LoggerClient) v
2 - (v instanceof LoggerClient
3 - ((v instanceof LoggerClient) ? ((LoggerClient)v) : this)
4 - caller = ((v instanceof LoggerClient) ? ((LoggerClient)v) : this);
The cast (LoggerClient) v is, in this case not necessary.
Here you can find operator precedence:
http://java.sun.com/docs/books/tutorial/java/nutsandbolts/expressions.html