Declaring a PrintWriter object

[Malcolm Whitely]

Hi everyone,
I am trying to declare a new PrintWriter object as so:
PrintWriter pw= = new PrintWriter(OutputStream out);
which appears correct, but on compiling I get the 4 error message including:
") expected" and "cannot resolve symbol"
I've also tried "PrintWriter pw = new PrintWriter(Writer out, boolean autoFlush)" but to no avail.
Hope someone can help.

[Chad McGowan]

You need to create a PrintWriter by initializing it with an instance of OutputStream. Something like this:

FileOutputStream out = new FileOutputStream("c:\log.txt");
PrintWriter writer = new PrintWriter(out);

Then you can do what you want with your writer.

[Malcolm Whitely]

Thanks for your reply. Am I right in thinking that PrintWriter can be used alongside the println method to print characters on screen? If so, then how would the code differ?
One other thing, I tried the code you suggested but get a NullPointerException when I try to write a a string to the output file.
Thanks in advance and looking forward to hear from you.
[ February 20, 2003: Message edited by: Malcolm Whitely ]

[Chad McGowan]

Here's something I just threw together that should give you an idea.

import java.io.*;
public class OutPut
{
public static void main(String[] args)
{
try
{

OutputStream out = new FileOutputStream("c:\\log.txt");
PrintWriter writer = new PrintWriter(out);
writer.println("Hello");
writer.flush();
}
catch(Exception e)
{
e.printStackTrace();
}
}
}

As for your println question:
System.out.println(String x) prints to the standard output stream, which is a PrintStream.
The System class provides a static instance of this PrintStream for convenience, so you can call System.out.println();

[Malcolm Whitely]

Thanks again for the reply. It cleared out a few things for me.
At the moment, I've got a main() method and an output() method, which writes the contents of an array to a file. I've tried passing in my PrintWriter object from the main() method but the writing never seems to occur from within the output() method.
Here is my code:

//--------------------------
//output()
//--------------------------
public void output(PrintWriter pwrtr, String[] text)
{
   int counter=0;

while(text[counter]!=null) //displays only fields that are not null in the array
{
   pwrtr.println("text is: " + text[counter]);
   //pwrtr.write(text[counter]);
   pwrtr.println(text[counter]);
             counter++;
}
}

//--------------------------
//main()
//--------------------------
public static void main(String args[])
{
TextHandlerImpl textHandler = new TextHandlerImpl();
File file = null; //create a new File object
String[] lines = new String[1000];

//---------------------------------
PrintWriter writer=null;

try
{
   //create an output stream to a file
   OutputStream out = new FileOutputStream("log.txt");   
                   writer = new PrintWriter(out);
   writer.println("Hello");
   writer.flush();
}
catch(Exception e)
{
   e.printStackTrace();
}
//---------------------------------
textHandler.output(writer,lines); //pass in printWriter object and 'lines' array
}

System.out.println() works fine in output() but pwrtr.println() doesn't. Another thing worth mentioning is that "Hello" which is executed in main() is written to file.
Thanks for the help. I really appreciate it.
[ February 21, 2003: Message edited by: Malcolm Whitely ]

[Chad McGowan]

I see a couple of problems right off. First, you don't have any data in the String[] that is passed to your output method. Second, even if you have data, you aren't flushing the writer, so you still won't get anything.
I modified your code a little. Take a look at it and note the things I changed.

public class OutPutTest {
    public OutPutTest()
    {
    }
   public void output(PrintWriter pwrtr, String[] text)
   {
       for (int i = 0; i < text.length; i++)
       {
           pwrtr.println("text is: " + text[i]);
           pwrtr.println(text[i]);
       }
       pwrtr.flush();
    }
           public static void main(String args[])
           {
                   OutPutTest textHandler = new OutPutTest();
                   PrintWriter writer=null;
                   try
                   {
                       OutputStream out = new FileOutputStream("c:\\testlog.txt");
                       writer = new PrintWriter(out);
                       writer.println("Hello");
                       writer.flush();
                   }
                   catch(Exception e)
                   {
                       e.printStackTrace();
                   }
                   textHandler.output(writer,args);
           }
}

[Malcolm Whitely]

That worked great Chad! As you suggested, the flush() method, which I have since read about, was the reason the data was not written to file.
I have noticed that the Java API is not as kind to beginners as Microsoft's MSDN which elaborately explains everything. Is there a book, more of a reference one with breakdowns of packages and classes, that you would recommend?

Thanks and best regards.
Malcolm
[ February 21, 2003: Message edited by: Malcolm Whitely ]

[Chad McGowan]

Thinking in Java gives some nice examples for some of the more commonly used classes. The link is to a free html version. When I started learning java, I read it, along with Core Java I and II.
Once you get the hang of how to use the Java Documentation, you will find it more useful.
Good Luck