NullPointerException with String

[debraj mallick]

hi all,

my code is like

        URL me= new URL("http://en.wikipedia.org/wiki/Java_(programming_language)");
        BufferedReader in = new BufferedReader(new InputStreamReader(me.openStream()));
        String myHtml;
        while ((myHtml = in.readLine()) != null) {
            System.out.println(myHtml); // works fine
        }
        System.out.println("my string : "+myHtml.toString()); // getting java.lang.NullPointerException
        in.close();

the exception which i am getting is

Exception in thread "main" java.lang.NullPointerException
        at com.debraj.main(debraj.java:20)

all i need is to print the entire string.

[Jeff Verdegan]

Of course this line:

        System.out.println("my string : "+myHtml.toString()); // getting java.lang.NullPointerException  

is giving you NPE. You know that myHtml is null, because otherwise you would not have gotten out of the loop. So of course myHtml.toString() must give NPE.

debraj mallick wrote:
all i need is to print the entire string.

You mean the full HTML that you read in the loop? And you want to print the whole thing out after the loop exits? Then you have to build up a string or other data structure that holds the whole thing. Right now, your loop says:

Read a line.
Store it in myHtml.
Print myHtml.

Read a line.
Store it in myHtml (replacing whatever was there before).
Print myHtml.

And keep doing that until myHtml holds null, because that's what we put into it after reading the final line.

Inside the loop you could use StringBuilder.append(), or, if you still need access to the individual lines, java.util.List.add().

[debraj mallick]

StringBuilder sb = new StringBuilder();
while ((myHtml = in.readLine()) != null) {
            sb.append(myHtml);
        }

thanks that really solved my problem

[Jeff Verdegan]

You're very welcome! Glad you got it sorted out!