I always thought that Predef.println
was merely a shortcut for System.out.println
, but apparently I am mistaken, since it doesn't seem to use System.out
at all. Why is that so? And how can I do the "redirecting" of System.out
be开发者_StackOverflow中文版low in Scala?
scala> val baos = new java.io.ByteArrayOutputStream
baos: java.io.ByteArrayOutputStream =
scala> val ps = new java.io.PrintStream(baos)
ps: java.io.PrintStream = java.io.PrintStream@6c5ac4
scala> System.setOut(ps)
scala> println("hello")
hello
scala> new String(baos.toByteArray)
res2: java.lang.String = ""
scala> System.out.println("hello")
scala> new String(baos.toByteArray)
res7: java.lang.String =
"hello
"
Predef.println
is shortcut for Console.println
and you can use Console.setOut
or Console.withOut
for redirecting.
Also, Console.setOut
only affects the current thread while System.setOut
affects the whole JVM. Additionally Scala 2.9 repl
evaluates each line in its own thread, so Console.setOut
is not usable there.
scala> val baos = new java.io.ByteArrayOutputStream
baos: java.io.ByteArrayOutputStream =
scala> Console.withOut(baos)(print("hello"))
scala> println(baos)
hello
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