Bug in Roundup Q. 127

[Ted Velkoff]

Either the if statement should read (b == true)
or another answer choice should be given (does not compile)
------------------
Ted Velkoff

[Carl Trusiak]

Originally posted by Ted Velkoff:
Either the if statement should read (b == true)
or another answer choice should be given (does not compile)

Nothing prevents you from doing an assignment or even a making a method call in an if statement. Java processes any call or assignments first so it's actually the same as writing
b=true;
if(b)
{
The restriction in java is that assignments or calls must result in a boolean result(and not an integer result)

[Ted Velkoff]

Yes, Carl,
You are correct. The part of the question that surprised me was not that a boolean expressions could be used, but rather that assignment in Java is an expression. In Pascal/Ada/Eiffel, assignment is a statement. I thought that the C idiom of
int i = 5;
if (i = 0) ...
was prohibited in Java by virtue of assignment being a statement. Instead it is prohibited by requiring the AssignmentExpression to have type boolean.
Thanks.

------------------
Ted Velkoff

[paul wheaton]

Tony, if you use your ftp access, you can find the file that has the actual question in it and post it here so we can know what we are discussing.

[paul wheaton]

Question: (#127)Given this code, what prints? boolean b = false; if (b = true) {System.out.println("yes");}

Answer: "Yes" prints because the expression (b = true) uses the assignment operator =, not the equality operator ==. So b is set to true, and the result is true so the if condition runs the code.
I made the following program:

public class Equals
{
    public static void main( String[] args )
    {
        boolean b = false ;
        if ( b = true )
        {
            System.out.println( "yes!" );
        }
    }
}

And it compiled fine. When I run it, I see "yes!"
So, is the question okay as is?

[Ted Velkoff]

Originally posted by Paul Wheaton:
And it compiled fine. When I run it, I see "yes!"
So, is the question okay as is?
[/B]

Yes, the question is OK. I was too fast on the trigger to post my question, but learned another thing about Java along the way. Thanks.