regex - How to replace java code block to another code block automatically or pragramatically? -

i have many java source files in want change code block code block in every java files have in project.

e.g. project has 300 java source file , every file has code block

while (p.getcurrenttoken() != jsontoken.end_object) {     p.nexttoken();     field = p.getcurrentname();     obj.populatefromjsonstring(field, p); }  

i want replace code block

while (p.nexttoken() != null) {     field = p.getcurrentname();     if(field!=null){         obj.populatefromjsonstring(field, p);     } } 

in java files. object obj in code block different different files

i know somehow can done text processing sed , awk. thinking alternate solution way compilers read , parse java source file. there may application based on way solving problem.

please share way or application solve problem. sed/awk based solutions welcome.

it's best use ide this, if wanted use sed, put in file called j.sed

/while (p\.getcurrenttoken() != jsontoken\.end_object) {/{     :loop     n     /}/b         s/field = p\.getcurrentname();/if (field!=null) {/     s/p\.nexttoken();/field = p\.getcurrentname();/     s/...\.populatefromjsonstring(field, p);/\t&\n\t}/     b loop } 

then use in command line

find . -type f -name '*.java' -exec sed -i.bak -f j.sed {} \; 

this on input:

while (p.getcurrenttoken() != jsontoken.end_object) {     p.nexttoken();     field = p.getcurrentname();     obj.populatefromjsonstring(field, p); }  

output this:

while (p.getcurrenttoken() != jsontoken.end_object) {     field = p.getcurrentname();     if (field!=null) {         obj.populatefromjsonstring(field, p);     } }  

the -i.bak edit in place , store backup filename.java.bak