In this java code that some one else has written, people have used null check condition as null!=abc or null==abc, but I need to change it to abc!=null and abc==null respectively.
Someone told me that this can be done using regular expressions very easily, as till now I was performing a manual task, but searching it and then replacing it manually.
I do not know all the requirements for what could be on the right side of the boolean expression, but assuming it is a variable name, \w will be a roughly accurate search (see http://download.oracle.com/javase/tutorial/java/nutsandbolts/variables.html for the full specification of variable names).
Search string:
null\s*([!=]=)\s*(\w+)
Replace string
$1 $2 null
\s+ with \s* to match also the examples given by OP.
+.
$2 $1 null, and more over this works only with simple conditions, not for complex conditions. I am also reading the same, and will comment once i am able to find something.It cannot be done correctly with regular expressions.
Consider
/*
Print whether null==abc.
*/
System.out.print("null==abc : " + (null==abc));
If you want to change only the code, the third null==abc above, then you can get unintended changes to string and comment content by naively using regular expression replaces to change code.
And you want to be careful to not change
null==abc.def
to
abc==null.def
or to change
null==abc(def)
to
abc==null(def)
If you're OK with potential string and comment changes, and are going to review the changes to make sure you didn't break any method calls, then you can always do this in perl.
perl -i.bak -pe 's/null(\s*[!=]=\s*)([\w.]+)/$2$1null/g' YourJavaFile.java
null==abctoabc=null? Those have two different meanings (hint hint, one is assignment)