Scala: Append on list to other list with reassignment: Reassignment to val error

Question

I know i can concat two lists a & b to result c like this in scala. But how can i do same thing if i do not want extra variable c and hold result in variable a.

 val a = List(1,2,3)
 val b = List(4,5,6)
 val c = a ::: b (I do not want this extra variable c and want to hold result in val a only)

Basically appending List b to List a:
Something like [ a = a ::: b]
This is giving me error: Reassignment to val.

Answer 1

A val is final. Once a value has been assigned to it ( List(1,2,3) ), a new value cannot be reassigned to it. Use a var

Answer 2

Use var instead of val . val can't be re-assigned.

Answer 3

You can treat it as a:::b anywhere in your code . BUT note that even if you define a new val c = a:::b it does not allocate more memory size (as the size of a and b ). it uses data sharing of a and b so it good practice to create a new val if it makes your code more readable (or makes your life easier) otherwise just use a:::b . in general it is a better practice than using a 'var'