Question

I’m wondering what the best way to fix precision errors is in Java. As you can see in the following example, there are precision errors:

class FloatTest
{
  public static void main(String[] args)
  {
    Float number1 = 1.89f;
    
    for(int i = 11; i < 800; i*=2)
    {
      System.out.println("loop value: " + i);
      System.out.println(i*number1);
      System.out.println("");
    }
  }
}

The result displayed is:

loop value: 11

20.789999

loop value: 22

41.579998

loop value: 44

83.159996

loop value: 88

166.31999

loop value: 176

332.63998

loop value: 352

665.27997

loop value: 704

1330.5599

Also, if someone can explain why it only does it starting at 11 and doubling the value every time. I think all other values (or many of them at least) displayed the correct result.

Problems like this have caused me headache in the past and I usually use number formatters or put them into a String.

Edit: As people have mentioned, I could use a double, but after trying it, it seems that 1.89 as a double times 792 still outputs an error (the output is 1496.8799999999999).

I guess I’ll try the other solutions such as BigDecimal

Answer 1

If you really care about precision, you should use BigDecimal

https://docs.oracle.com/javase/8/docs/api/java/math/BigDecimal.html

https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/math/BigDecimal.html