Dart double Data Type by Examples

In this tutorial, we learn how to use double-precision floating point number data type in Dart programming language.

How to declare double variables and basic operators in Dart

void main() {
  double number1 = 10.5;
  double number2 = 5.5;

  double addResult = number1 + number2;
  double subtractResult = number1 - number2;
  double multuplyResult = number1 * number2;
  double divisionResult = number1 / number2;
  double moduloResult = number1 % number2;

  print("10.5 + 5.5 = " + addResult.toString());
  print("10.5 - 5.5 = " + subtractResult.toString());
  print("10.5 * 5.5 = " + multuplyResult.toString());
  print("10.5 / 5.5 = " + divisionResult.toString());
  print("10.5 % 5.5 = " + moduloResult.toString());
}
The output is: 
10.5 + 5.5 = 16.0
10.5 - 5.5 = 5.0
10.5 * 5.5 = 57.75
10.5 / 5.5 = 1.9090909090909092
10.5 % 5.5 = 5.0

Check a double value is negative or not using isNegative property

void main() {
  double number1 = -10.0;
  double number2 = -0.0;
  double number3 = 0.0;
  double number4 = 10.0;

  print(number1.isNegative);
  print(number2.isNegative);
  print(number3.isNegative);
  print(number4.isNegative);
}
The output is: 
true
true
false
false

Get absolute value of a double variable using abs() method

void main() {
  double number1 = -5;
  double number2 = 5;

  print(number1.abs());
  print(number2.abs());
}
The output is: 
5.0
5.0

How to use ceil() method

Dart’s double class provides ceil() method to return the least integer no smaller than a given double value. 

void main() {
  double number1 = 5.5;
  double number2 = 5.1;

  print(number1.ceil());
  print(number2.ceil());
}
The output is: 
6
6

How to use ceilToDouble() method

Dart’s double class provides ceilToDouble() method to return the least integer double value no smaller than a given double value. 

void main() {
  double number1 = 5.5;
  double number2 = 5.1;

  print(number1.ceilToDouble());
  print(number2.ceilToDouble());
}
The output is: 
6.0
6.0

How to use floor() method

Dart’s double class provides floor() method to return the greatest integer no greater than a given double value. 

void main() {
  double number1 = 5.5;
  double number2 = 5.1;

  print(number1.floor());
  print(number2.floor());
}
The output is: 
5
5

How to use floorToDouble() method

Dart’s double class provides floorToDouble() method to return the greatest integer double value no greater than a given double value. 

void main() {
  double number1 = 5.5;
  double number2 = 5.1;

  print(number1.floorToDouble());
  print(number2.floorToDouble());
}
The output is: 
5.0
5.0

How to use round() method

Dart’s double class provides round() method to return the integer value closest to the given double value. 

void main() {
  double number1 = 5.5;
  double number2 = 5.1;

  print(number1.round());
  print(number2.round());
}
The output is: 
6
5

How to use roundToDouble() method

Dart’s double class provides roundToDouble() method to return the integer double value closest to the given double value. 

void main() {
  double number1 = 5.5;
  double number2 = 5.1;

  print(number1.roundToDouble());
  print(number2.roundToDouble());
}
The output is: 
6.0
5.0

How to use truncate() method

Dart’s double class provides truncate() method to return the integer obtained by discarding any fractional digits from the given double value. 

void main() {
  double number1 = 5.5;
  double number2 = 5.1;

  print(number1.truncate());
  print(number2.truncate());
}
The output is: 
5
5

How to use truncateToDouble() method

Dart’s double class provides truncateToDouble() method to return the double integer obtained by discarding any fractional digits from the given double value. 

void main() {
  double number1 = 5.5;
  double number2 = 5.1;

  print(number1.truncateToDouble());
  print(number2.truncateToDouble());
}
The output is: 
5.0
5.0

How to use compareTo() method

The double’s compareTo() method returns a negative number if the value is less than the compare to value, zero if it equals and return positive number if it is greater than the compare to value. 

void main() {
  double number1 = 5.5;
  double number2 = 10.5;

  print(number1.compareTo(number2));
  print(number1.compareTo(5.5));
  print(number1.compareTo(1.0));
  print((-0.0).compareTo(0.0));
}
The output is: 
-1
0
1
-1

How to use remainder() method

The double’s remainder() method to return the remainder of the truncating division of 2 double values. 

void main() {
  double number1 = 10;
  double number2 = 3;

  print(number1.remainder(number2));
}
The output is: 
1.0

Convert double value to integer value in Dart

The double’s toInt() method to truncate the double value and return as an integer value. 

void main() {
  double number = 10.5;

  print(number.toInt());
}
The output is: 
10

Convert double value to String value in Dart

Using toString() method 

void main() {
  double number = 200.123;

  print(number.toString());
}
The output is: 
200.123

Using toStringAsExponential() method 

void main() {
  double number = 200.123;

  print(number.toStringAsExponential(1));
  print(number.toStringAsExponential(2));
  print(number.toStringAsExponential(3));
  print(number.toStringAsExponential(4));
}
The output is: 
2.0e+2
2.00e+2
2.001e+2
2.0012e+2

Using toStringAsFixed() method 

void main() {
  double number = 200.123;

  print(number.toStringAsFixed(1));
  print(number.toStringAsFixed(2));
  print(number.toStringAsFixed(3));
  print(number.toStringAsFixed(4));
}
The output is: 
200.1
200.12
200.123
200.1230

Parse a String to a double value

Using parse() static method 

void main() {
  double number1 = double.parse("10.5");
  double number2 = double.parse("-10.5");
  double number3 = double.parse("  5.");
  double number4 = double.parse("  .5  ");
  double number5 = double.parse("-1.e5");
  double number6 = double.parse("1234E+7");
  double number7 = double.parse("+.12e-9");
  double number8 = double.parse("-NaN");

  print(number1);
  print(number2);
  print(number3);
  print(number4);
  print(number5);
  print(number6);
  print(number7);
  print(number8);
}
The output is: 
10.5
-10.5
5.0
0.5
-100000.0
12340000000.0
1.2e-10
NaN

Using tryParse() static method 

void main() {
  double number1 = double.tryParse("10.5");
  double number2 = double.tryParse("-10.5");
  double number3 = double.tryParse("  5.");
  double number4 = double.tryParse("  .5  ");
  double number5 = double.tryParse("-1.e5");
  double number6 = double.tryParse("1234E+7");
  double number7 = double.tryParse("+.12e-9");
  double number8 = double.tryParse("-NaN");

  print(number1);
  print(number2);
  print(number3);
  print(number4);
  print(number5);
  print(number6);
  print(number7);
  print(number8);
}
The output is: 
10.5
-10.5
5.0
0.5
-100000.0
12340000000.0
1.2e-10
NaN

The double’s constants

void main() {
  print(double.minPositive);

  print(double.maxFinite);

  print(double.infinity);

  print(double.negativeInfinity);

  print(double.nan);
}
The output is: 
5e-324
1.7976931348623157e+308
Infinity
-Infinity
NaN

Happy Coding 😊

Dart integer Data Type by Examples

Dart bool Data Type by Examples

Dart String Data Type by Examples

Dart StringBuffer by Examples

Dart RegExp by Examples

Tags:
Dart double