Scala ListBuffer

A list is a collection which contains immutable data. List represents linked list in Scala. A List is immutable, if we need to create a list that is constantly changing, the preferred approach is to use a ListBuffer.
The Scala List class holds a sequenced, linear list of items. A List can be built up efficiently only from back to front. the ListBuffer object is convenient when we want to build a list from front to back. It supports efficient prepend and append operations.

Once we are done creating our list, call the toList method. To convert the ListBuffer into a List, Time taken will be constant. To use ListBuffer, scala.collection.mutable.ListBuffer class is imported, an instance of ListBuffer is created.

Example :

var name = new ListBuffer[datatype]()  // empty buffer is created

var name = new ListBuffer("class", "gfg", "geeksforgeeks")

In the above example, first, an empty buffer is created here datatype indicates the type of data such as integer, string. Then created a buffer with three elements, of type string.

Below operation can be performed on ListBuffer –

• By using L += e we can appends the element e in constant time.
• By using e +=: L we can prepends the element e in constant time.
• L.toList In constant time, It returns a list with the contents of the ListBuffer . We should not use the ListBuffer once changing it to a list.

Operations on ListBuffer

Creating instance of ListBuffer:

// Scala program to create a ListBuffer
// ListBuffer class is imported
import scala.collection.mutable.ListBuffer

// Creating object
object GfG
{

    // Main Method
    def main(args: Array[String])
    {
        // Instance of ListBuffer is created
        var name = ListBuffer[String]()
        name += "GeeksForGeeks"
        name += "gfg"
        name += "Class"
        println(name)
    }
}

Output:

ListBuffer(GeeksForGeeks, gfg, Class)

Access element from ListBuffer:

Element is accessed same as list, ListBuffer(i) is used to accessed i^th index element of list.

// Scala program to access element of ListBuffer
// ListBuffer class is imported
import scala.collection.mutable.ListBuffer

// Creating Object
object GFG
{

    // Main Method
    def main(args: Array[String])
    {
        // Instance of ListBuffer is created
        var name = ListBuffer[String]()
        name += "GeeksForGeeks"
        name += "gfg"
        name += "Class"

        // Accessing 1th index element of listBuffer
        println(name(1))
    }
}

Output:

gfg

Adding elements in ListBuffer:

• Add single element to the buffer

  ListBuffer+=( element)

• Add two or more elements (method has a varargs parameter)

   ListBuffer+= (element1, element2, ..., elementN )

• Append one or more elements (uses a varargs parameter)

  ListBuffer.append( elem1, elem2, ... elemN)

// Scala program to add element in ListBuffer
// ListBuffer class is imported
import scala.collection.mutable.ListBuffer

// Creating Object
object GFG
{

    // Main Method
    def main(args: Array[String])
    {
        // Instance of ListBuffer is created
        var name = ListBuffer[String]()

        // Adding one element
        name += "GeeksForGeeks"

        // Add two or more elements
        name += ("gfg", "class")

        // Adding one or more element using append method
        name.append("Scala", "Article")

        // Printing ListBuffer
        println(name)
    }
}

Output:

ListBuffer(GeeksForGeeks, gfg, class, Scala, Article)

Deleting ListBuffer Elements:

• Remove one element

  ListBuffer-= (element)

• Remove multiple elements

  ListBuffer-= (elem1, elem2, ....., elemN)

// Scala program to delete element from ListBuffer
// ListBuffer class is imported
import scala.collection.mutable.ListBuffer

// Creating Object
object GFG
{

    // Main Method
    def main(args: Array[String])
    {
        // Instance of ListBuffer is created
        var name = ListBuffer( "GeeksForGeeks", "gfg",
                                "class", "Scala",
                                "Article" )

        // Deletes one element
        name -= "GeeksForGeeks"

        // Deletes two or more elements
        name -= ("gfg", "class")

        // Printing resultant ListBuffer
        println(name)
    }
}

Output:

ListBuffer(Scala, Article)

Deleting ListBuffer Elements using ListBuffer.remove() :

The remove() method is used to delete one element by its position in the ListBuffer, or a series of elements beginning at a starting position.

// Scala program for remove method, on ListBuffer
// ListBuffer class is imported
import scala.collection.mutable.ListBuffer

// Creating Object
object GFG
{

    // Main Method
    def main(args: Array[String])
    {
        // Instance of ListBuffer is created
        var name = ListBuffer( "GeeksForGeeks",
                                "gfg", "class",
                                "Scala", "Article" )

        // Removing 0th index element
        name.remove(0)

        // Printing resultant ListBuffer
        println(name)
        name.remove(1, 3)

        // Printing resultant ListBuffer
        println(name)
    }
}

Output:

ListBuffer(gfg, class, Scala, Article)
ListBuffer(gfg)