Keyboard Input

[Smita Chopra]

I have made a simple program to read from the keyboard

  public class Keyboard {
 
public static void main(String[] args) {
          
          String val;
          BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
          try {
             while((val = br.readLine()) != null) {
                System.out.println(val);          
            }
         }catch(IOException i) {
               i.printStackTrace();
         }
} 
}

The problem is that when I write null on the console it doesn't terminate the program even though thats what i am using in the while condition.
Thanks

[Mishra Anshu]

while((val = br.readLine()) != null) 
   {
   System.out.println(val);
   }

br.readLine() returns the contents of a line, not including any line termination chracters or null if the end of the stream has reached.

so, when you type at the console "null", it is not the null object but it is the string "null".
The String "nul" is not a null object.
null means something that doesn't exist.

Hope it helps.

[Smita Chopra]

Originally posted by Mishra Anshu:

while((val = br.readLine()) != null) 
   {
   System.out.println(val);
   }

br.readLine() returns the contents of a line, not including any line termination chracters or null if the end of the stream has reached.

so, when you type at the console "null", it is not the null object but it is the string "null".
The String "nul" is not a null object.
null means something that doesn't exist.

Hope it helps.

Thanks for replying.
In that case shouldn't this work

while((val = br.readLine()) != "null") {
System.out.println(val);

But it doesn't work.
Even tried with something like
while((val = br.readLine()) != "stop") {
System.out.println(val);

and then wrote "stop" on the console (without quotes), but it doesn't work.

[Mishra Anshu]

This is what you want to do perhaps:--

public class Keyboard { 
public static void main(String[] args) {
String val;          
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

 try {
   while(!((val = br.readLine())).equalsIgnoreCase("null")) 
   {
   System.out.println("["+val+"]");
   }
 }catch(IOException i) {
  i.printStackTrace();
  }
 }
}

Please see how two strings are compared.
Is it OK now?

[Smita Chopra]

Originally posted by Mishra Anshu:
This is what you want to do perhaps:--

public class Keyboard { 
public static void main(String[] args) {
String val;          
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

 try {
   while(!((val = br.readLine())).equalsIgnoreCase("null")) 
   {
   System.out.println("["+val+"]");
   }
 }catch(IOException i) {
  i.printStackTrace();
  }
 }
}

Please see how two strings are compared.
Is it OK now?

THanks a lot

[Mishra Anshu]

[Stan James]

See if typing Ctrl-Z gives you a null on that readln(). Let us know.