# const keyword in Dart Programming

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Dart provides us with two ways in which we can declare variables with fixed values. One of them is by declaring a variable with a const keyword, and the other is by declaring the variable with a final keyword.

It should be noted that both of them does provide an assurance that once a value is assigned to the variable with them, it won't change, but indeed they are slightly different from one another.

## const

A variable that is declared using the const keyword cannot be assigned any other value. Also, the variable is known as a compile-time constant, which in turn means that its value must be declared while compiling the program.

### Example

Consider the example shown below -

Live Demo

void main(){
const name = "mukul";
print(name);

const marsGravity = 3.721;
print(marsGravity);
}

### Output

mukul
3.721

If we try to assign any other value to any of the two variables declared above, the compiler will throw an error.

### Example

Consider the example shown below -

void main(){
const name = "mukul";
print(name);

name = "mayank";
print(name);
}

### Output

Error: Can't assign to the const variable 'name'.
name = "mayank";
^^^^
Error: Compilation failed.

It should also be noted that we can declare Objects at compile-time and assign them to a constant variable.

### Example

Consider the example shown below −

Live Demo

import 'dart:math';
void main(){
const Rectangle bounds = const Rectangle(0, 0, 3, 4);
print(bounds);
}

### Output

Rectangle (0, 0) 3 x 4
Updated on 21-May-2021 12:44:52