Number formatting helps make your numbers more readable. : Number Format « Data Type « Java Tutorial

1. Java Tutorial
2. Data Type
3. Number Format

import java.text.NumberFormat;
import java.util.Locale;

public class MainClass {
  public static void main(String[] args) {
    NumberFormat nf = NumberFormat.getInstance(Locale.US);
    System.out.println(nf.getClass().getName());
    System.out.println(nf.format(123445));
  }
}

java.text.DecimalFormat
123,445

1. If you use Locale.Germany, you'll get a NumberFormat object that formats numbers according to the German locale.
2. If you pass Locale.US, you get one for the US number format.
3. The no-argument getInstance method returns a NumberFormat object with the user computer's locale.