OutputStream to InputStream

outToIn.scala

import java.io.OutputStreamWriter
import java.io.{PipedInputStream, PipedOutputStream, ByteArrayOutputStream, PrintStream}
import java.io.{BufferedReader, InputStreamReader}
import org.apache.commons.io.output.TeeOutputStream


import scala.{App => SApp}

object TestOut extends SApp {
  val orig = System.out

  val in  = new PipedInputStream()
  val out = new PipedOutputStream(in)

  val tee = new TeeOutputStream(orig, out)
  System.setOut(new PrintStream(tee))

  new Thread(new Runnable {
    val reader = new BufferedReader(new InputStreamReader(in))
    override def run(): Unit = {
      var line: String = null
      while ({
        line = reader.readLine()
        line != null
      }) {
        System.err.println(s">> $line")
      }
    }
  }).start()

  Thread.sleep(1000)

  while (true) {
    System.out.println("abc")
    Thread.sleep(1000)
  }
}


object TestPipe extends SApp {
  val in  = new PipedInputStream()
  val out = new PipedOutputStream(in)


  new Thread(new Runnable {
    val w = new OutputStreamWriter(out)

    override def run(): Unit = {
      while (true) {
        w.write("abc\n")
        w.flush()
        Thread.sleep(1000)
      }
    }
  }).start()

  val reader = new BufferedReader(new InputStreamReader(in))
  var line: String = null

  while ({
    line = reader.readLine()
    line != null
  }) {
    println(line)
  }
}