Why aren't variables declared in "try" in scope in "catch" or "finally"?
- by Jon Schneider
In C# and in Java (and possibly other languages as well), variables declared in a "try" block are not in scope in the corresponding "catch" or "finally" blocks. For example, the following code does not compile:
try {
String s = "test";
// (more code...)
}
catch {
Console.Out.WriteLine(s); //Java fans: think "System.out.println" here instead
}
In this code, a compile-time error occurs on the reference to s in the catch block, because s is only in scope in the try block. (In Java, the compile error is "s cannot be resolved"; in C#, it's "The name 's' does not exist in the current context".)
The general solution to this issue seems to be to instead declare variables just before the try block, instead of within the try block:
String s;
try {
s = "test";
// (more code...)
}
catch {
Console.Out.WriteLine(s); //Java fans: think "System.out.println" here instead
}
However, at least to me, (1) this feels like a clunky solution, and (2) it results in the variables having a larger scope than the programmer intended (the entire remainder of the method, instead of only in the context of the try-catch-finally).
My question is, what were/are the rationale(s) behind this language design decision (in Java, in C#, and/or in any other applicable languages)?
