Two questions.

[matthew meltzer]

The first question is what do I need to do to fix the following code?

class Q24{
  public static void main(String[] args) throws A{
    try{
      f();
    
    }catch(A e){ throw e; }
finally{ System.out.println("Done.");
}
 }
  public static void f() throws B{
    throw new B();
 
}
 
class A extends Throwable{}
class B extends A{}

The error I am getting says that it reached the end of the file while parsing. What am I doing wrong?

The other question has to do with understanding the following code and what I am being asked to do.

public class Q21{
  public static void main(String[] args){
    try{
      if(args.length == 0) return;
      System.out.println(args[0]);
    }finally{
     System.out.println("That's all folks!");
    }
  }
}

"Can any errors or exceptions occur from the user failing to input arguments at runtime, or by putting certain arguments in at runtime? What will print if the user inputs nothing?
What will print if the user inputs an argument or several arguments?"


I don't understand what I am supposed to do.

[Bear Bibeault]

matthew meltzer wrote:The first question is what do I need to do to fix the following code?

Better indentation would allow you to see what's missing. Try properly indenting the code and see how the braces match up.

[Campbell Ritchie]

And have you really been told to call classes things like Q21? That is a very poor name for a class.

[Tony Docherty]

"Can any errors or exceptions occur from the user failing to input arguments at runtime, or by putting certain arguments in at runtime? What will print if the user inputs nothing?
What will print if the user inputs an argument or several arguments?"

I don't understand what I am supposed to do.

What exactly are you stuck on? You just have to imagine you are running the code from the command line with or without some command line parameters and then work out what the code will do in each case.

[William P O'Sullivan]

What if args is null ?

WP

[Campbell Ritchie]

How on earth could args be null in a main method?

[Jesper de Jong]

When you post questions from a book, mock exam or some other source, then please tell us where you copied them from - QuoteYourSources.

[Rajdeep Biswas]

Campbell Ritchie wrote:How on earth could args be null in a main method?

Why not? Without any arguments passed while executing the class, the String[] blocks will have null or not?

[Stuart A. Burkett]

Rajdeep Biswas wrote:Why not? Without any arguments passed while executing the class, the String[] blocks will have null or not?

No. It will be an empty array. i.e. args.length will be zero.

[Winston Gutkowski]

Rajdeep Biswas wrote:Why not? Without any arguments passed while executing the class, the String[] blocks will have null or not?

Not. It would be a 0-length array.

Winston

[Rajdeep Biswas]

Winston Gutkowski wrote:

Rajdeep Biswas wrote:Why not? Without any arguments passed while executing the class, the String[] blocks will have null or not?

Not. It would be a 0-length array.

Winston

Hi Winston,

I can think of 2 situations:

1. No args passed, the array is not constructed. So no question at all about its properties as the array does not exists!
OR
2. The args array has String type blocks, and the default value of String is NULL. So args[0].hashCode() [any instance method or else] will return a NullPointerException

[Stuart A. Burkett]

Rajdeep Biswas wrote:1. No args passed, the array is not constructed. So no question at all about its properties as the array does not exists!

Yes it does. If no arguments are passed the array exists and has a length of zero.

[R. Jain]

Rajdeep Biswas wrote:
I can think of 2 situations:

1. No args passed, the array is not constructed. So no question at all about its properties as the array does not exists!
OR
2. The args array has String type blocks, and the default value of String is NULL. So args[0].hashCode() [any instance method or else] will return a NullPointerException

Why not just print args in your main, and take a look what it prints..
You will get a nice looking hashcode telling you that its not null.

[Campbell Ritchie]

You cannot get a null element in the command‑line arguments. You can pass new String[]{null, null, null}, but that array reference does not point to null. It is in fact the same as new String[3].