Convert 1 to 01

Question

I have an int between 1 - 99. How do I get it to always be a double digit, ie: 01, 04, 21?

Answer 1

Presumably you mean to store the number in a String.

Since JDK1.5 there has been the String.format() method, which will let you do exactly what you want:

String s = String.format("%02d", someNumber); 

One of the nice things about String.format() is that you can use it to build up more complex strings without resorting to lots of concatenation, resulting in much cleaner code.

String logMessage = String.format("Error processing record %d of %d: %s", recordNumber, maxRecords, error); 

Answer 2

Yet another way

String text = (num < 10 ? "0" : "") + num; 

EDIT: The code is short enough that the JIT can compile it to nothing. ;)

long start = System.nanoTime(); for(int i=0;i<100000;i++) {     for(int num=1;num<100;num++) {         String text = (num < 10 ? "0" : "") + num;     } } long time = System.nanoTime() - start; System.out.println(time/99/100000); 

prints

0