A float type data turning string in Java

Java.text.Numberformat Formater = java.text.decimalformat.getInstance ();

Formater.SetMaximumumfractionDigits (2);

Formater.setminimumfractiondigits (2);

Formater.format (a);

[In the masterpiece of Magicxxxxxxxx (MAGIC):]

: float a = 3.7777777777

: How to cut off as a string 3.78? ?