String in Dart

String In Dart

String data types help you to store text data. In string, you can represent your name, address, or even the entire complete text of the book. It is used to hold a series or sequence of characters – letters, numbers, and special characters. You can use single or double or triple quotes to represent string.

Example

void main() {   
   String text1 = 'This is an example of a single-line string.';   
   String text2 = "This is an example of a double-quotes multiline line string.";   
   String text3 = """This is a multiline line   
string using the triple-quotes.""";   
   print(text1);  
   print(text2);   
   print(text3);   
}
Show Output

String Concatenation

You can combine one string with another string. This is called concatenation. In Dart, you can use the + operator or use interpolation to concatenate the string. Interpolation makes it easy to read and understand the code.

Example

void main() {   
String firstName = "John";
String lastName = "Doe";
print("Using +, Full Name is "+firstName + " " + lastName.);
print("Using interpolation, fulname is $firstName $lastName.");  
  
}
Show Output

Properties Of String

  • codeUnits: Returns an unmodifiable list of the UTF-16 code units of this string.
  • isEmpty: Returns true if this string is empty.
  • isNotEmpty: Returns false if this string is empty.
  • Length: Returns the length of the string including space, tab, and newline characters.

String Properties Example In Dart

void main() {
   String str = "Hi";
   print(str.codeUnits);   //Example of code units
   print(str.isEmpty);     //Example of isEmpty
   print(str.isNotEmpty);  //Example of isNotEmpty
   print("The length of the string is: ${str.length}");   //Example of Length
}
Show Output

Methods Of String

  • toLowerCase(): Converts all characters in this string to lowercase.
  • toUpperCase(): Converts all characters in this string to uppercase.
  • trim(): Returns the string without any leading and trailing whitespace.
  • compareTo(): Compares this object to another.
  • replaceAll(): Replaces all substrings that match the specified pattern with a given value.
  • split(): Splits the string at matches of the specified delimiter and returns a list of substrings.
  • toString(): Returns a string representation of this object.
  • substring(): Returns the substring of this string that extends from startIndex, inclusive, to endIndex, exclusive.
  • codeUnitAt(): Returns the 16-bit UTF-16 code unit at the given index.

String Methods Example In Dart

Here you will see various methods example, that can help your work a lot better and fast.

Converting String To Uppercase and Lowercase

You can convert your text to lower case using .toLowerCase() and convert to uppercase using .toUpperCase() method.

//Example of toUpperCase() and toLowerCase()
void main() { 
   String address1 = "Florida"; // Here F is capital
   String address2 = "TexAs"; // Here T and A are capital
   print("Address 1 in uppercase: ${address1.toUpperCase()}"); 
   print("Address 1 in lowercase: ${address1.toLowerCase()}"); 
   print("Address 2 in uppercase: ${address2.toUpperCase()}"); 
   print("Address 2 in lowercase: ${address2.toLowerCase()}"); 
}
Show Output

Trim String In Dart

Trim is helpful when removing leading and trailing spaces from the text. This trim method will remove all the starting and ending spaces from the text.

Info

Note: In dart, trim() method doesn’t remove spaces in the middle.

//Example of trim()
void main() { 
  String address1 = " USA"; // Contain space at leading.
  String address2 = "Japan  "; // Contain space at trailing. 
  String address3 = "New Delhi"; // Contains space at middle.
  
  print("Result of address1 trim is ${address1.trim()}");
  print("Result of address2 trim is ${address2.trim()}");
  print("Result of address3 trim is ${address3.trim()}");

}
Show Output

Compare String In Dart

In dart, you can compare two strings. It will give result 0 when two texts are equal, 1 when the first string is greater than the second, and -1 when the first string is smaller than the second.

//Example of compareTo()
void main() { 
   String item1 = "Apple"; 
   String item2 = "Ant"; 
   String item3 = "Basket"; 
   
   print("Comparing item 1 with item 2: ${item1.compareTo(item2)}"); 
   print("Comparing item 1 with item 3: ${item1.compareTo(item3)}"); 
   print("Comparing item 3 with item 2: ${item3.compareTo(item2)}"); 
} 
Show Output

Replace String In Dart

You can replace one value with another with the replaceAll(“old”, “new”) method in dart. It will replace all the “old” words with “new”. Here in this example, this will replace milk with water.

//Example of replaceAll()
void main() { 
String text = "I am a good boy I like milk. Doctor says milk is good for health.";
  
String newText = text.replaceAll("milk", "water"); 
 
print("Original Text: $text");
print("Replaced Text: $newText");  
   
} 
Show Output

Split String In Dart

If you want to split String by comma, space, or other text, you can use the dart split method. It will help you to split String to list.

//Example of split()
void main() { 
  String allNames = "Ram, Hari, Shyam, Gopal";

  List<String> listNames = allNames.split(",");
  print("Value of listName is $listNames");

  print("List name at 0 index ${listNames[0]}");
  print("List name at 1 index ${listNames[1]}");
  print("List name at 2 index ${listNames[2]}");
  print("List name at 3 index ${listNames[3]}");
   
} 
Show Output

ToString In Dart

In dart, toString() represents String representation of the value/object.

//Example of toString()
void main() { 
int number = 20;     
String result = number.toString(); 
  
print("Type of number is ${number.runtimeType}");  
print("Type of result is ${result.runtimeType}");  
    
}   
Show Output

SubString In Dart

When you want to get text from any position then you can use substring in dart.

//Example of substring()
void main() { 
   String text = "I love computer"; 
   print("Print only computer: ${text.substring(7)}"); // from index 6 to the last index 
   print("Print only love: ${text.substring(2,6)}");// from index 2 to the 6th index 
} 
Show Output

Reverse String In Dart

If you want to reverse string in dart, you can reverse it by using different solution. One solution is here.

void main() { 
  String input = "Hello"; 
  print("$input Reverse is ${input.split('').reversed.join()}"); 
} 
Show Output