Scala: ArrayBuffer

ArrayBuffer is a variable-length array. It is similar to ArrayList in Java.

 

Syntax

var/val variableName = new ArrayBuffer[DataType]

 

Example

val arrayBuffer1 = new ArrayBuffer[Int]

 

To use ArrayBuffer, you should import the below package.

scala.collection.mutable.ArrayBuffer

scala> import scala.collection.mutable.ArrayBuffer
import scala.collection.mutable.ArrayBuffer

scala> val arrayBuffer1 = new ArrayBuffer[Int]
val arrayBuffer1: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer()

How to add an element to ArrayBuffer?

Use + operator to add an element to the array.

scala> arrayBuffer1 += 2
val res136: arrayBuffer1.type = ArrayBuffer(2)

scala> arrayBuffer1 += 3
val res137: arrayBuffer1.type = ArrayBuffer(2, 3)

scala> arrayBuffer1 += 5
val res138: arrayBuffer1.type = ArrayBuffer(2, 3, 5)

scala> print (arrayBuffer1)
ArrayBuffer(2, 3, 5)

How to add elements from an Array to ArrayBuffer?

Use ++ operator.

scala> arrayBuffer1 ++= Array(7, 11, 13)
val res143: arrayBuffer1.type = ArrayBuffer(2, 3, 5, 7, 11, 13, 7, 11, 13)

How to remove an element from ArrayBuffer?

Use remove(index) method to remove the element at a specific index from ArrayBuffer.

scala> print(arrayBuffer1)
ArrayBuffer(2, 3, 5, 7, 11, 13, 7, 11, 13)
scala> 

scala> arrayBuffer1.remove(3)
val res145: Int = 7

scala> arrayBuffer1.remove(7)
val res146: Int = 13

scala> print(arrayBuffer1)
ArrayBuffer(2, 3, 5, 11, 13, 7, 11)

How to insert an element at a specific index?

Use insert(index, element) method to insert an element at a specific index.

scala> print(arrayBuffer1)
ArrayBuffer(2, 3, 5, 11, 13, 7, 11)

scala> arrayBuffer1.insert(2, 123456)

scala> print(arrayBuffer1)
ArrayBuffer(2, 3, 123456, 5, 11, 13, 7, 11)

How get an array from ArrayBuffer?

Use toArray method.

scala> var arr1 = arrayBuffer1.toArray
var arr1: Array[Int] = Array(2, 3, 123456, 5, 11, 13, 7, 11)

How to get ArrayBuffer from an Array?

Use toBuffer method.

scala> var arrayBuffer2 = arr1.toBuffer
var arrayBuffer2: scala.collection.mutable.Buffer[Int] = ArrayBuffer(2, 3, 123456, 5, 11, 13, 7, 11)

Find sum of elements of ArrayBuffer?

‘sum’ function is used to get the sum of all the elements of ArrayBuffer.

scala> ArrayBuffer(2, 3, 5, 7).sum
val res158: Int = 17

Find the maximum element in an ArrayBuffer

Use ‘max’ function.

scala> ArrayBuffer(2, 30, 51, 7).max
val res160: Int = 51

Sort the elements of ArrayBuffer

Use ‘sorted’ function. This method does not sort in place, it returns completely new ArrayBuffer with sorted data.

scala> val buffer1 = ArrayBuffer(2, 30, 51, 7)
val buffer1: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(2, 30, 51, 7)

scala> val buffer2 = buffer1.sorted
val buffer2: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(2, 7, 30, 51)

scala> println(buffer1)
ArrayBuffer(2, 30, 51, 7)

scala> println(buffer2)
ArrayBuffer(2, 7, 30, 51)

Reverse the elements of ArrayBuffer

Use ‘reverse’ function to reverse the elements of ArrayBuffer.

scala> var buffer1 = ArrayBuffer(2, 30, 51, 7)
var buffer1: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(2, 30, 51, 7)

scala> var buffer2 = buffer1.reverse
var buffer2: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(7, 51, 30, 2)

scala> buffer1
val res172: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(2, 30, 51, 7)

scala> buffer2
val res173: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(7, 51, 30, 2)

Print elements of ArrayBuffer using a separator

Use ‘mkString’ method to get a string that has elements of ArrayBuffer where each element is separated by given separator.

scala> var res = buffer1.mkString(",")
var res: String = 2,30,51,7

scala> println(res)
2,30,51,7

Separate elements using |.

scala> res = buffer1.mkString("|")
// mutated res

scala> println(res)
2|30|51|7

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