Scala: Why java.lang.IllegalArgumentException: Cannot format given Object as a Date?

Question

I have the following simple code that leads to a RuntimeException error that I can't explain:

import java.text.MessageFormat
import java.util.Date
import org.apache.commons.cli._
import org.joda.time._
import org.joda.time.format.DateTimeFormat

object TestMain {
  def doFormat(value: Any): String = {
    val ClassOfDouble = classOf[Double]
    val ClassOfDate = classOf[Date]
    val ClassOfDateTime = classOf[DateTime]
    val result: String = value.getClass match {
      case ClassOfDouble => MessageFormat.format("{0,number,#.####################}", Array(value.asInstanceOf[DateTime]))
      case ClassOfDate => MessageFormat.format("{0,date,yyyy.MM.dd}", Array(value.asInstanceOf[Date]))
      case ClassOfDateTime => DateTimeFormat.forPattern("yyyy.MM.dd HH:mm:SSS").print(value.asInstanceOf[DateTime])
      case _ => value.toString
    }
    result
  }

  def main(args: Array[String]): Unit = {
    println(doFormat(new Date()))
  }
}

... and the resulting runtime error:

Exception in thread "main" java.lang.IllegalArgumentException: Cannot format given Object as a Date
    at java.text.DateFormat.format(Unknown Source)
    at java.text.Format.format(Unknown Source)
    at java.text.MessageFormat.subformat(Unknown Source)
    at java.text.MessageFormat.format(Unknown Source)
    at java.text.Format.format(Unknown Source)
    at java.text.MessageFormat.format(Unknown Source)
    at test.TestMain$.doFormat(TestMain.scala:28)
    at test.TestMain$.main(TestMain.scala:39)
    at test.TestMain.main(TestMain.scala)

user7605325 · Accepted Answer · 2017-10-17 12:07:51Z

3

This happens because you're passing an Array to the format method. You can simply use the Date directly:

case ClassOfDate => MessageFormat.format("{0,date,yyyy.MM.dd}", value.asInstanceOf[Date])

With this, the output will be:

2017.10.17

answered Oct 17, 2017 at 12:07

user7605325

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Comments

Illia Smolii · Accepted Answer · 2017-10-17 12:14:27Z

3

You don't need to wrap the second argument of the MessageFormat.format() with an Array since it requires a vararg.

Call with Array is confusing. It is unclear if Array is vararg (Object...) or just a first argument of vararg (Object). It uses the second and you encounter with an Exception.

answered Oct 17, 2017 at 12:14

Illia Smolii

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