How do I define this constant?

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JS - 24 Nov 2004 20:33 GMT

Based on the following:

int x = ((int)(bound * Math.random()));
int z = ((int)(bound * Math.random()));

String b =
JOptionPane.showInputDialog("What is " + x + " times " + z + " ?");
int guess = new Integer(b).intValue();

boolean test2 = (guess == (x * z));

String q = "correct";
String p = "incorrect";

I would like to make the following constant, k:

String k = if (test2 == true)
System.out.print(q);
else
System.out.print(p);

But is that not possible? I get the following error:

Error: illegal start of expression

js

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Boudewijn Dijkstra - 24 Nov 2004 21:19 GMT

> Based on the following:
>
[quoted text clipped - 20 lines]
>
> Error: illegal start of expression

That is because an if-block doesn't return a value. Also, the
System.out.print method prints characters to the console (the standard
output), not to a string. I suggest the following statement:

String k = test2 ? p : q;

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Eric Sosman - 24 Nov 2004 21:26 GMT

> Based on the following:
>
[quoted text clipped - 16 lines]
> else
> System.out.print(p);

I think what you want is

    String k = (test2 == true) ? q : p;
    System.out.print(k);

or more simply

    String k = test2 ? q : p;
    System.out.print(k);

or more simply still

    System.out.print(test2 ? q : p);

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Eric.Sosman@sun.com

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Oscar kind - 24 Nov 2004 21:33 GMT

> I would like to make the following constant, k:
>
> String k = if (test2 == true)
> System.out.print(q);
> else
> System.out.print(p);

This cannot be done using an if-statement; you'll ahve to use an
expression. Luckily, there is one: the ternary operator ?: :

String k = (test2 == true) ? q : p;

or simply:
String k = test2 : q : p;

Note however, that this can easily become unreadable. So unless it is for
something trivial like the example above, I'd not use it.

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Hal Rosser - 25 Nov 2004 02:41 GMT

> I would like to make the following constant, k:
>
> String k = if (test2 == true)
> System.out.print(q);
> else
> System.out.print(p);

String k = p;
if (test2 ){ k = q; }
(But then, its not a constant)
If I recall correctly, Constants are assigned their value at compile time,
but variables are assigned their values at run time - so you can't assign a
variable to a constant.
this would not work
public const String K = p;

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JS - 25 Nov 2004 11:42 GMT

Thank you all for introducing me with the ternary operator ?: . It now works
but I am still a bit confused about what ? means and what : means.

Js

> Based on the following:
>
[quoted text clipped - 22 lines]
>
> js

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Chris Smith - 25 Nov 2004 14:39 GMT

> Thank you all for introducing me with the ternary operator ?: . It now works
> but I am still a bit confused about what ? means and what : means.

Those two characters are not separate operators; they are part of one
expression. You MUST write something like:

<condition> ? <exp1> : <exp2>

And then here's what happens:

1. <condition> is evaluated as a boolean expression
2. If <condition> is true, then <exp1> becomes the result
3. If <condition> is false, then <exp2> becomes the result

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V S Rawat वी एस रावत - 25 Nov 2004 17:42 GMT

> Thank you all for introducing me with the ternary
> operator ?: . It now works but I am still a bit confused
> about what ? means and what : means.
>
> Js

That is the syntax.

k = test2 ? p : q;

test2 is evaluated first.

if test2 evaluates to true, k will be assigned the first
value p.

if test2 evaluates to false, k will be assigned the second
value q.

it is equivalent to the following:

if (test2) {
k = p;
}
else {
k = q;
}

it is just a shorthand. it will get very confusing if test2,
p or q are lengthy statements. hence, avoid using = ? :
operator, and use the above compelete good old "if then
else" until you are comfortable.

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Rawat

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Eric Sosman - 29 Nov 2004 22:38 GMT

> Thank you all for introducing me with the ternary operator ?: . It now works
> but I am still a bit confused about what ? means and what : means.

`?' means `then' and `:' means `else', more or less.
That's actually the way the ternary operator was spelled
in Algol, where you could write (IIRC)

x := if a then b else c;

In Java, this is written as

x = a ? b : c;

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How do I define this constant?

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