Floating point display in Java

Java two digits left after decimal point
Double NUM1 = 11;

Double num2 = 21;

String num3 = "";
The function can determine the display format of the decimal number: percent, limited decimal point, scientific counting method, etc.
#: integer digit 0: decimal digits
DecimalFormat df = new DecimalFormat ("0"); Show integers
num3 = Df.format ((num1-num2)/num2*100);
System.out.println (NUM3);

DecimalFormat df1 = new DecimalFormat ("###.0"); Displays three-bit integers, one decimal
num3 = Df1.format ((num1-num2)/num2*100);
System.out.println (NUM3);

DecimalFormat DF2 = new DecimalFormat ("###.000"); Displays three-bit integers, three decimal places
num3 = Df2.format ((num1-num2)/num2*100);
System.out.println (NUM3);

DecimalFormat df3 = new DecimalFormat ("0.000E00"); Display scientific notation, corresponding format
num3 = Df3.format ((num1-num2)/num2*100);
System.out.println (NUM3);

Floating point display in Java