strange array

[Poyz]

i got this error, it seems like an array but it gives an error when i try to push()

var str = tempRow.getItem("stri")
var arr = str.split(",")
trace (arr.length) //output 19
arr.push("hello")

output

12:26:10.593 - [ WARNING ] > Error in extension [ main.as ]: Java class
"java.lang.Object" has no public instance field or method named "19". (main.as#1257) Line: 268

[Poyz]

and the solution was few topics down here -_-

String(tempRow.getItem("stri"))