toPrint vs toString

toPrint vs toString

[Andrew Cagney]

toString(): for dumping internal object state
---------------------------------------------

Just a reminder; Java's Object class includes a <<public String 
toString()>> method that can be overridden (by default it prints the 
object's address and type) to dump out an objects internal state.  That 
way, when printing or tracing this method is called vis:

    System.out.println("my " + task); // uses Task.toString
    logger.log(Level.FINE, "{0} task\n", task); // ditto

and debugging level information is provided.  However, within frysk, 
toString() or variations shouldn't be used when creating output intended 
for the user.

toPrint(): for displaying an object user friendly
-------------------------------------------------

If the output is intended for the user, the add a toPrint() method and 
use that.  There are two variations.  The first sends the output to a 
Writer vis:

    public void toPrint(PrintWriter writer) ... writer.print ...

and the second, if you find it necessary, just wraps the first vis:

    public void toPrint()
        stringWriter = new StringBuffer()
        printWriter = new PrintWriter(stringWriter)
        toPrint(printWriter)
        return stringWriter.toString();
 
For instance, frysk.value.Value as methods such as:

    public void toPrint(PrintWriter writer, ByteBuffer memory, Format 
format)
    public String toPrint() { ... see above ... }

for converting a value in to a user-readable form.

Re: toPrint vs toString

[Sami Wagiaalla]

>    public void toPrint()
>        stringWriter = new StringBuffer()
>        printWriter = new PrintWriter(stringWriter)
>        toPrint(printWriter)
>        return stringWriter.toString();
this should be stringWriter.getBuffer().toString();

Re: toPrint vs toString

[Kris Van Hees]

On Tue, Aug 14, 2007 at 11:35:31AM -0400, Sami Wagiaalla wrote:
>
>>    public void toPrint()
>>        stringWriter = new StringBuffer()
>>        printWriter = new PrintWriter(stringWriter)
>>        toPrint(printWriter)
>>        return stringWriter.toString();
> this should be stringWriter.getBuffer().toString();

Hm, more like:

public String toPrint() {
    StringWriter stringWriter = new StringWriter();
    PrintWriter printWriter = new PrintWriter(stringWriter);

    toPrint(printWriter);

    return stringWriter.toString();
}

because:
	1) You cannot pass a StringBuffer to PrinterWriter's contructor
	2) StringBuffer doesn't have a getBuffer() method
	3) StringWriter has a toString() method
	4) You can't return a String from a method that declares its return
	   type as 'void' obviously

Either way perhaps it is safer in cases like this to point to existing code
(that is known to compile, etc) as an example on how to use specific
constructs?

	Cheers,
	Kris

Re: toPrint vs toString

[Sami Wagiaalla]

Sami Wagiaalla wrote:
>
>>    public void toPrint()
>>        stringWriter = new StringBuffer()
>>        printWriter = new PrintWriter(stringWriter)
>>        toPrint(printWriter)
>>        return stringWriter.toString();
> this should be stringWriter.getBuffer().toString();
>
nm... I thought I was saving people from a trap I fell into but it looks 
like it works.
my bad.

Sami