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 ith 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)
