Question

I’m working to create an array of instances of the class in itself.

class A (arg: Int) {
    var a1 = new Array[A] (arg)
    ....
}

declaring it this way gives “java.lang.NullPointerException” during run-time. Is there any way to remove this exception?

Answer 1

I’m sure that you are trying to access elements of array a1 later in your code. There you get your exception.

I’ve prepared small chunk of code to demonstrate it:

class A (arg: Int) {
    var a1=new Array[A] (arg)   
    def giveMeException(){
      println(a1(0).a1.length)
    }
}
object Program  extends App {
    val noExceptionA = new A(2);
    noExceptionA.a1(0) = new A(0);
    noExceptionA.a1(1) = new A(0);
    val exceptionA = new A(2);

    // Will print 0
    noExceptionA.giveMeException();

    // Will throw  java.lang.NullPointerException
    exceptionA.giveMeException();   
}