Scala : Error in sorting

Question

I have a class defined as below :

class VocabWord(cn1: Int = 0, word1: String = null)  {
   var cn = cn1
   var word = word1         
}

and also there exists an array as below :

var vocab = new Array[VocabWord](100)

Now, when I perform an operation like this below :

vocab = vocab.sortWith((x, y) => x.cn < y.cn)

I am getting an null pointer exception.

please use CamelCase for class names. vocab_word is an eyesore, the convention is to write VocabWord. _ is already too far overloaded in Scala! — Kevin Wright
– Kevin Wright, Commented Feb 19, 2014 at 18:46

Kyle · Accepted Answer · 2014-02-20 01:08:56Z

3

You are initializing the array with 100 null's

var vocab = new Array[VocabWord](100) // Array(null, null, null.....)

You can't apply the method cn to null

var vocab = Array[VocabWord](new VocabWord(100), new VocabWord(3))
vocab.sortWith( (x, y) => x.cn < y.cn)
// Array(VocabWord@49ac9ae3, VocabWord@21a4c98e)

edited Feb 20, 2014 at 1:08

answered Feb 19, 2014 at 18:35

Kyle

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Comments

Lee · Accepted Answer · 2014-02-19 18:37:31Z

1

If you want to create an array with new elements in, you can use Array.init:

val vocab = Array.fill[vocab_word](100)(new vocab_word)

at present you are creating an array containing 100 null references.

answered Feb 19, 2014 at 18:37

Lee

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