positivePrefix property Null safety

1. Flutter
2. intl
3. NumberFormat
4. positivePrefix property

NumberFormat class

1. Constructors
2. NumberFormat
3. compact
4. compactCurrency
5. compactLong
6. compactSimpleCurrency
7. currency
8. currencyPattern
9. decimalPattern
10. decimalPercentPattern
11. percentPattern
12. scientificPattern
13. simpleCurrency
14. Properties
15. currencyName
16. currencySymbol
17. decimalDigits
18. hashCode
19. locale
20. localeZero
21. maximumFractionDigits
22. maximumIntegerDigits
23. minimumExponentDigits
24. minimumFractionDigits
25. minimumIntegerDigits
26. multiplier
27. negativePrefix
28. negativeSuffix
29. positivePrefix
30. positiveSuffix
31. runtimeType
32. significantDigits
33. significantDigitsInUse
34. symbols
35. Methods
36. format
37. noSuchMethod
38. parse
39. simpleCurrencySymbol
40. toString
41. turnOffGrouping
42. Operators
43. operator ==
44. Static methods
45. localeExists
46. numberOfIntegerDigits