A String object is immutable, i.e. a String cannot be changed once created. In situations where you need to perform repeated modifications to a string, we need StringBuilder class. StringBuilder is utilized to append input data to the internal buffer. We can perform numerous operations with the support of methods on the StringBuilder. This operation comprises appending data, inserting data, and removing data.
important points:

• The StringBuilder class is beneficent for mutable strings to extend effectively.
• The instance of StringBuilder is utilized like a String.
• Strings of Scala are immutable so, when you require a mutable String then you can use StringBuilder.

• Appending character: This operation is helpful in appending character.
  Example:
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  // Scala program to append // a character    // Creating object  object GFG {        // Main method     def main(args: Array[String])     {            // Creating StringBuilder          val x = new StringBuilder("Author");            // Appending character          val y = (x += 's')            // Displays the string after          // appending the character          println(y)     } }

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  Output:

  Authors
  

  Here, (x += ‘ ‘) is utilized to append a character.

• Appending String: This operation is helpful in appending string.
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  // Scala program to append // a String    // Creating object  object GFG {        // Main method     def main(args: Array[String])     {            // Creating StringBuilder          val x = new StringBuilder("Authors");            // Appending String          val y = (x ++= " of GeeksforGeeks")            // Displays the string after          // appending the string          println(y)        } }

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  Output:

  
  

  
  

  Authors of GeeksforGeeks
  

  Here, (x ++= ‘ ‘) is utilized to append String.

• Appending String representation of number: Here, the number can be of any type like Integer, Double, Long, Float, etc.
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  // Scala program to append // String representation  // of number    // Creating object  object num {        // Main method     def main(args: Array[String])     {            // Creating StringBuilder          val x = new StringBuilder("Number of Contributors : ");            // Appending String          // representation of number          val y = x.append(800)            // Displays the string after          // appending the number         println(y)     } }

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  Output:

  Number of Contributors : 800
  

  Here, x.append(n) is utilized to append the String representation of the number, where ‘n’ is the number of any type.

• Resetting the content of the StringBuilder: It is helpful in resetting the content by making it empty.
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  // Scala program to reset  // the content    // Creating object  object GFG {        // Main method     def main(args: Array[String])     {            // Creating StringBuilder          val x = new StringBuilder("Hello")            // Resetting the content          val y = x.clear()             // Displays empty content         println(y)     } }

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  Output:

  ()
  

  Here, x.clear() is utilized to clear the content of the StringBuilder.

• Delete operation: This operation is helpful in deleting characters from the content of the StringBuilder.
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  // Scala program to perform  // delete operation    // Creating object  object delete {        // Main method     def main(args: Array[String])     {            // Creating StringBuilder          val q = new StringBuilder("Computer Science")            // Deleting characters          val r = q.delete(1, 3)             // Displaying string after          // deleting some characters         println(r)     } }

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  Output:

  Cputer Science
  

  Here, q.delete(i, j) is utilized to delete the character indexed from i to (j – 1).

• Insertion operation: This operation is helpful in inserting Strings.
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  // Scala program to perform  // insertion operation    // Creating object  object insert {        // Main method     def main(args: Array[String])     {            // Creating StringBuilder          val q = new StringBuilder("GfG CS portal")            // inserting strings          val r = q.insert(4, "is a " )             // Displays string after          // insertion of required          // string         println(r)     } }

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  Output:

  GfG is a CS portal
  

  Here, q.insert(i, “s”) is utilized to insert the String (s) at index i.

• Converting StringBuilder to a String: StringBuilder can be converted to a String using this operation.
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  // Scala program of Converting  // StringBuilder to a String    // Creating object  object builder {        // Main method     def main(args: Array[String])     {            // Creating StringBuilder          val q = new StringBuilder("GeeksforGeeks")            // Applying conversion          // operation          val r = q.toString            // Displays String         println(r)     } }

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  Output:

  GeeksforGeeks
  

  Here, q.toString is utilized to convert StringBuilder to a string.