ArrayIndexOutofBoundException In Scala Program Usind VTD-XML
import java.lang._
import com.ximpleware._
object Sample {
def main(args :Array[String])= {
// println("helloo")
try{
var i :Int = -1
val vgen :VTDGen= new VTDGen()
val ap :AutoPilot =new AutoPilot()
ap.selectXPath("CATALOG/CD/COUNTRY/text()")
if(vgen.parseFile("../catalog.xml", false)) {
val vnav :VTDNav = vgen.getNav()
ap.bind(vnav)
while((i=ap.evalXPath)!= -1) {
println(vnav.toString(i))
println(vnav.toNormalizedString(vnav.getText()))
}
ap.resetXPath()
}
}
catch {
case e :Exception => println(e)
}
}
}
I have imported VTD-XML Library It compiles Well but On Execution prints an Exception
:java.lang.ArrayIndexOutOfBoundsException: -1
I have solved the while issue in 开发者_Python百科the code. But the problem is I always get -1 for ap.evalXPAth
I believe the answer lies in the line
while((i=ap.evalXPath)!= -1) {
In Scala assignment returns Unit (equivalent to void in Java) and hence this loop cannot terminate. For example the program as follows loops infinitely
scala> var i = 0
i: Int = 0
scala> while((i = i + 1) != 10) { println(i) }
<console>:7: warning: comparing values of types Unit and Int using `!=' will always yield true
while((i = i + 1) != 10) { println(i) }
As John McCrae said; the while check will not fly in scala. Instead you can define a new while construction like this for -1-ending calls:
def whileNotEmpty(whileF: () => Int)(doF: (Int) => Unit): Unit = {
val n = whileF()
if (n != -1) {
doF(n)
whileNotEmpty(whileF)(doF)
}
}
This is a simplified example of an invocation that read from the keyboard until you give -1:
whileNotEmpty(() => Console.readLine.toInt) {
n => println(n)
}
精彩评论