NullPointerException with String

[John Paterson]

Hi Folks,

I have this doubt.

String x =  null;
System.out.print(x.toString());
System.out.print(x);

In the above code, x.toString gives a NullPointerException. I believe this is due to the reference variable x not pointing anywhere as it's declared null.
That being the case, why is the line System.out.print(x) printing null to the console? Hope someone can explain why this difference. Thanks.

[Paul Anilprem]

John Paterson wrote:Hi Folks,

I have this doubt.

String x =  null;
System.out.print(x.toString());
System.out.print(x);

In the above code, x.toString gives a NullPointerException. I believe this is due to the reference variable x not pointing anywhere as it's declared null.
That being the case, why is the line System.out.print(x) printing null to the console? Hope someone can explain why this difference. Thanks.

Accessing a null reference always causes the JVM to throw NPE.
The print method simply checks the input for null before invoking toString on it. If the input is null, it prints "null". That is why there is no NPE.

[Jain Amit]

Hi,

Following is the Java implementation ref.. http://www.docjar.com/html/api/java/io/PrintStream.java.html

public void print(String s) {
666 if (s == null) {
667 s = "null";
668 }
669 write(s);

So if s is null, "null" string is printed. I hope it helps.

Thanks
Amit

[John Paterson]

Hi guys,

Thanks for reply. Appreciate it.