Java：异常处理中的未知错误

Question

i have a weird question. i had a quiz in my class today. One portion of the quiz was to find and correct errors in a short piece of code. one of the questions was like this

 class Example {
    public static void main(String[] args) {
        try {
            System.out.println("xyz");
        } catch (Exception e) {
            System.out.println("Exception caught");
        } finally {
            System.out.println("abc");
        }
    }
 }

I thought there was no error in the program but my professor insisted that there was. Can anyone guess what the error is?

Answer 1

The "error" may be that you don't need to handle any exception here: System.out.println does not specify any checked exception. It could simply be:

public static void main(String[] args) {        
     System.out.println("xyz");        
}

Since the Exception class covers both checked and unchecked exceptions, then if you add a catch block here, in this case you would be handling only unchecked exceptions, which you should not normally handle.

Answer 2

There is no Error in the Above Program , but also there is no need to put a try{} catch{} ....since you don't use any code that can throw an Exception , for example a risky method like Thread.sleep();

So maybe that's what your professor meant .

Answer 3

Well, I see nothing that would keep this from compiling, but I do see some problems. To begin with, there are comments indicating the presence of code which is not there. Comments out of sync with code is always a problem. [EDIT: indentation errors have been edited away] And you're catching Exception e, which you really oughtn't to do. You should always catch a specific exception that you expect to encounter, and handle it specifically. Since there's no exception that System.out.println can throw, this would make the whole Exception handling block a problem.

Answer 4

The following code snippet would throw a compilation error if used with IOException , since System.out.println would never throw an IOException but could throw Exception or Throwable which is its super class.

try {
    System.out.println("xyz");
} catch (IOException e) {
    //simple display error statement here
} finally {
    //simple print statement here
}