How To Deal With String Value Of Null In Data File

I have table data I'm trying to read . However one column is populated with the word "null". I guess java does not like dealing with the word null and throws errors.
 
When I try a block like : if ( rsrow.getString(insCol) = "null") {

I get and error .
 
If I try :
 
cmp = rsrow.getString(insCol);If I try:If I try:
if (cmp = "null") {

I get an error
 
If I try to use a replace function like:
 
System.out.println(cmp.replace("null", "0"));

Just to see if replace works I get and error.
 
What is the BEST way to replace this string value with something like "0"  when I come across it with out jave throwing an error? I want it such that every time I come across the word "null" I can repalce it with "0".
 
Something like:
 
if (rsrow.getString(insCol) = "null") {rowofdata = rowofdata + "'0',";  } else {rowofdata = rowofdata + "'" + rsrow.getString(insCol) + "',";}