Scala程序Usind VTD-XML中的ArrayIndexOutofBoundException [英] ArrayIndexOutofBoundException In Scala Program Usind VTD-XML

问题描述

    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)
      }
     }
    }

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我已经导入了VTD-XML库 编译良好，但在执行时会显示异常

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I have imported VTD-XML Library It compiles Well but On Execution prints an Exception

:java.lang.ArrayIndexOutOfBoundsException: -1

我已经解决了代码中的while问题.但是问题是我总是ap.evalXPAth

I have solved the while issue in the code. But the problem is I always get -1 for ap.evalXPAth

推荐答案

我相信答案就在这行

while((i=ap.evalXPath)!= -1) {

在Scala赋值中返回Unit(在Java中等同于void)，因此此循环无法终止.例如下面的程序无限循环

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) }

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