rounding off values to 2 decimal places in java - java-7

Question

I am using Java 7 and I just want to round off values to 2 decimal places, sample code is also given from various stackoverflow links :
Double d1= 4.37 , d2=0.694444444; //expected result after multiplication of numbers d1 and d2 is 3.04
DecimalFormat df = new DecimalFormat("#.#####");
String str = df.format(d1*d2);
d=(Double)df.parse(str);
System.out.println(d);//Prints 3.03472
df = new DecimalFormat("#.####");
str = df.format(d);
d= (Double)df.parse(str);
System.out.println(d);//Prints 3.0347
df = new DecimalFormat("#.###");
str = df.format(d);
d= (Double)df.parse(str);
System.out.println(d);//Prints 3.035
df = new DecimalFormat("#.##");
str = df.format(d);
d= (Double)df.parse(str);
System.out.println(d); //Prints my desired result 3.04
Is it not possible to possible to do this in 2 or 3 statements.
Regards
Kris

Answer 1

The problem is that the expected result 3.04 makes no sense, if you round to the closest value it should be 3.03. The result of 4.37*0.694444444 is 3.03472222028 and that is closer to 3.03 then to 3.04:
abs 3.03472222028 - 3.03 = 0.00472222028
abs 3.03472222028 - 3.04 = 0.00527777972
So actually all you need is
new DecimalFormat("#.##");
But as Klitos says, you would probably want to keep the real value as long as possible, and only round if you have to persist it to the database. Where you could use
String.format("%.2f", value)
Update 17/11
With the example you provided:
DecimalFormat df = new DecimalFormat("#.##");
String result = df.format(10.85*1/1.44);
The result is 7.53 (correct).
However, with your code, the result is 7.54, which is wrong.
That is because you round every digit sequentially and the errors accumulate, resulting in a rounding error, as can be seen in the example you provided.
So you really don't need to write your own rounding algorithm.You can just use the default from new DecimalFormat("#.##").