Check my code that will work for integer and String.
Assume our first number is 129018. And we want to add zeros to that so the the length of final string will be 10. For that you can use following code
int number=129018;
int requiredLengthAfterPadding=10;
String resultString=Integer.toString(number);
int inputStringLengh=resultString.length();
int diff=requiredLengthAfterPadding-inputStringLengh;
if(inputStringLengh