为什么以下Java代码无法编译？

Question

Quite Frankly, I'm just not understanding what my instructor is asking me to do here. I've tried using "try - catch" blocks, as well as throws Exception in the method signature. I've read about checked and unchecked exceptions. I'm sure this will get voted down or closed, but can someone throw me a bone here? My instructors instructions are as follows:

"Correct it so it compiles."

class Exception3{
    public static void main(String[] args){         
    if (Integer.parseInt(args[0]) == 0)             
        throw new Exception("Invalid Command Line Argument");     
     } 
}

It's obvious that it is throwing a RuntimeException. More Specifically an ArrayIndexOutOfBoundsException. I know the cause of the exception is because the array is empty, so the referenced index doesn't exist. I mean, technically I could just erase if(Integer.parseInt(args[0]) == 0) and throw new Exception("Invalid Command Line Argument"); and replace it with System.out.println("It compiles now");

Any ideas?

Answer 1

public static void main(String[] args) throws Exception{         
    if (Integer.parseInt(args[0]) == 0)             
        throw new Exception("Invalid Command Line Argument");     
     } 

Your method throwing Exception , so method declaration should specify that it may throw Exception .

As per java tutorial

Checked exceptions are subject to the Catch or Specify Requirement. All exceptions are checked exceptions, except for those indicated by Error, RuntimeException, and their subclasses.

Answer 2

You have to either catch it using a try catch statement:

class Exception3 {
    public static void main(String[] args) {
        try {
            if (Integer.parseInt(args[0]) == 0)
                throw new Exception("Invalid Command Line Argument");
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
}

or declare it at the method header:

class Exception3 {
    public static void main(String[] args) throws Exception {
        if (Integer.parseInt(args[0]) == 0)
            throw new Exception("Invalid Command Line Argument");
    }
}