Before invoking any method of an object, a null check should be done.

Eg:

String str1 = null;
String str2 = "ASP";

str2 = str1.toUpperCase(); // Which will throw NullPointerException.

So I have to ensure that this line is in the if check. Like,

String str1 = null;
String str2 = "ASP";

if(str1 != null)
{
str2 = str1.toUpperCase();
}

Any help would be appreciated. Which would be better a Java rule or XPATH rule?