if i format a floating number which has number of actual decimal digits less than 6, then it adds trailing zeroes so that total number of actual decimal digits remain 6

val double1 = 1234.5678
println(String.format("%f", double1))  //1234.567800
println(String.format("%f", 1.2))      //1.200000
println(String.format("%f", 2.445))    //2.445000

what if we don’t need trailing zeroes? how would you approach?

You can use

DecimalFormat

instead of

String.format

to get access to more formatting options.

val formatter = DecimalFormat("#.######")
println(formatter.format(1234.5678)) // 1234.5678
println(formatter.format(1.2)) // 1.2
println(formatter.format(2.445)) // 2.445

The patterns are different from the string format ones, so look at the docs to see what options you have.

a solution may be replace "0+$" with ""

But that's complicating it even further. Start with the basics first, and keep it as simple as possible. It seems that

Double.toString()

already does what you want, so just do

println(number)

or, if you really need it to be inside a

String.format

you can use

String.format("%s", number)

(or preferably

"%s".format(number)

). If that doesn't do what you want, describe the problem in more detail.