Android Question Round and Round2 for Float data type

[Roberto P.]

Hello to all,
I have read many threads regarding the use of the round and round2 functions, but I do not understand which function is to be used to have a simple rounding of a value contained in a float variable.

I have a float variable that contains 103.70 and is converted with a periodic value (103.69999694824219). considering that this periodic value creates a misalignment of hundredths on the calculations, I thought to use the round functions to be sure to have the value with only two decimals.

But the situation does not change! Because?

What should I use to get a precise rounding?

Here are some examples and related results.

Dim aFloat As Float         = 103.70
    Dim aDouble As Double        = 103.70

    Log("Value of float " & aFloat)
    
    Dim aNewFloat As Float    = Round2(aFloat, 2)
    Log("a new float " & aNewFloat)
    
    Dim bNewFloat As Float    = aNewFloat
    Log("b new float " & bNewFloat)
    
    Dim cNewFloat As Float    = Round(aFloat)
    Log("c new float " & cNewFloat)
    
    Dim aNewDouble As Double    = Round2(aDouble, 2)
    Log("d anew double " & aNewDouble)

results

Value of float 103.69999694824219
a new float 103.69999694824219
b new float 103.69999694824219
c new float 104
d anew double 103.7

thank in advance
regards

 

[stevel05]

You cannot change the precision of the stored values of Floats or Doubles, Doubles are generally preferred to minimize rounding errors that Floats incur. To display a value with a specified precision you should use NumberFormat, or NumberFormat2

 

[Roberto P.]

Hi Stevel,

so I can not delete the decimals from the float and double variables? The problem is not the display of data but the calculations altered by decimals.

thank you

 

[stevel05]

Using Doubles instead of floats should minimize calculation issues.

 

[udg]

Another way could be to multiply/divide by 100 your original value and save it as long/int.
Something like:

dim mymoney as long = edittext1.text * 100 'assuming edittext contains  a valid decimal number

 

[Erel]

Don't use Round or Round2. Use double variables and convert the numbers to strings with NumberFormat.

If it is not good enough then switch to BigDecimal from agraham's BigNumber library.