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console.writeline and System.out.println Ask Question

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console.writeline and System.out.println Ask Question

What exactly is the technical difference between console.writeline and System.out.println? I know that System.out.println writes to standard output but is this not the same thing as the console?

I do not fully understand the documentation for console.writeline.

ベストアンサー1

Here are the primary differences between using System.out/.err/.in and System.console():

  • System.console() returns null if your application is not run in a terminal (though you can handle this in your application)
  • System.console() provides methods for reading password without echoing characters
  • System.out and System.err use the default platform encoding, while the Console class output methods use the console encoding

This latter behaviour may not be immediately obvious, but code like this can demonstrate the difference:

public class ConsoleDemo {
  public static void main(String[] args) {
    String[] data = { "\u250C\u2500\u2500\u2500\u2500\u2500\u2510", 
        "\u2502Hello\u2502",
        "\u2514\u2500\u2500\u2500\u2500\u2500\u2518" };
    for (String s : data) {
      System.out.println(s);
    }
    for (String s : data) {
      System.console().writer().println(s);
    }
  }
}

On my Windows XP which has a system encoding of windows-1252 and a default console encoding of IBM850, this code will write:

???????
?Hello?
???????
┌─────┐
│Hello│
└─────┘

Note that this behaviour depends on the console encoding being set to a different encoding to the system encoding. This is the default behaviour on Windows for a bunch of historical reasons.

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