What is the difference between ArrayBuffer and Array

Question

I\'m new to scala/java and I have troubles getting the difference between those two.

By reading the scala doc I understood that ArrayBuffer are made to

Answer 1

Another difference is in term of reference and value equality

Array(1,2) == Array(1,2)              // res0: Boolean = false
ArrayBuffer(1, 2) == ArrayBuffer(1,2) // res1: Boolean = true

The reason for the difference is == routes to .equals where Array.equals is implemented using Java's == which compares references

public boolean equals(Object obj) {
  return (this == obj);
}

whilst ArrayBuffer.equals compares elements contained by ArrayBuffer using sameElements method

  override def equals(o: scala.Any): Boolean = this.eq(o.asInstanceOf[AnyRef]) || (
    o match {
      case it: Seq[A] => (it eq this) || (it canEqual this) && sameElements(it)
      case _ => false
    }
  )

Similarly, contains behaves differently

Array(Array(1,2)).contains(Array(1,2))                   // res0: Boolean = false
ArrayBuffer(ArrayBuffer(1,2)).contains(ArrayBuffer(1,2)) // res1: Boolean = true