Convert integer to String Spring Controller

March 27, 2023

public ModelAndView showUserAppsByID(@PathVariable(name = "id") int id) {
   String emIDConvert= Integer.toString(id);

   // ...
}

This Controller format works but is not the same as what I expected.

Example:

id=3
id=43

My expectation:

id=0003
id=0043

That main I want to format Integer to String varchar(4).

>Solution :

Java has nothing like varchar, just a String of a variable length or a character array with a fixed length (char[4]). Practically, everybody uses String, unless the character array is specifically required (for example passwords).

You can use a simple static method String#format to introduce the leading zeroes.

 String emIDConvert = String.format("%04d", id));

Demo:

String.format("%04d", 3));      // returns 0003
String.format("%04d", 34));     // returns 0034
String.format("%04d", 345));    // returns 0345
String.format("%04d", 3456));   // returns 3456
String.format("%04d", 34567));  // returns 34567

This method uses the java.util.Formatter, and the JavaDoc links to its details here.