Arithmetic with doubleTag(s): String/Number

You may find that
System.out.println( 1.33 - 1.3 );
// output :  0.030000000000000027
The unexpected result is coming from the fact that internal floating-point number representation is not well suited for that kind of operation.

The easiest way to solve this limitation is to the BigDecimal class :

import java.math.BigDecimal;