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Dart Programming - String

Published May 08, 2020

The String data type represents a sequence of characters. A Dart string is a sequence of UTF 16 code units.

String values in Dart can be represented using either single or double or triple quotes. Single line strings are represented using single or double quotes. Triple quotes are used to represent multi-line strings



String  variable_name = 'value'  


String  variable_name = ''value''  


String  variable_name = '''line1 


String  variable_name= ''''''line1 



void main() { 
   String str1 = 'Single line string'; 
   String str2 = "Single line string"; 
   String str3 = '''Multiline line string'''; 
   String str4 = """Multiline line string"""; 



Single line string 
Single line string 
Multiline line string 
Multiline line string 


Strings are immutable. However, strings can be subjected to various operations and the resultant string can be a stored as a new value.

String Interpolation

The process of creating a new string by appending a value to a static string is termed as concatenation or interpolation. In other words, it is the process of adding a string to another string.

The operator plus (+) is a commonly used mechanism to concatenate / interpolate strings.


void main() { 
   String str1 = "Hello"; 
   String str2 = "Dart"; 
   String res = str1+str2; 
   print("The concatenated string : ${res}"); 



The concatenated string : HelloDart


We can use "${}" can be used to interpolate the value of a Dart expression within strings.


void main() { 
   int n=1+1; 
   String str1 = "The sum of 1 and 2 is ${n}"; 
   String str2 = "The sum of 2 and 3 is ${2+3}"; 



The sum of 1 and 2 is 3 
The sum of 2 and 3 is 5


String Properties

The properties listed in the following table are all read-only.

Sr.No Property & Description
1 codeUnits

Returns an unmodifiable list of the UTF-16 code units of this string.

2 isEmprty

Returns true if this string is empty.

3 length

Returns the length of the string including space, tab and newline characters.

Methods to Manipulate Strings

The String class in the dart: core library also provides methods to manipulate strings.

Sr.No Methods & Description
1 toLowerCase()

Converts all characters in this string to lower case.

2 toUpperCase()

Converts all characters in this string to upper case.



Returns the string without any leading and trailing whitespace.

4 compareTo()

Compares this object to another.

5 replaceAll()

Replaces all substrings that match the specified pattern with a given value.

6 split()

Splits the string at matches of the specified delimiter and returns a list of substrings.

7 subString()

Returns the substring of this string that extends from startIndex, inclusive, to endIndex, exclusive.

8 toString()

Returns a string representation of this object.



Returns the 16-bit UTF-16 code unit at the given index.

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