https://github.com/jruby/jruby/jruby-core: JRuby is the effort to recreate the Ruby (https://www.ruby-lang.org) interpreter in Java. (JRuby)
  • headius
  • enebo
  • wmeissner
  • BanzaiMan
  • mkristian 
package org.jruby.util.io;

public enum STDIO {

    IN, OUT, ERR;

    public int fileno() {
        switch (this) {
        case IN:
            return 0;
        case OUT:
            return 1;
        case ERR:
            return 2;
        default:
            throw new RuntimeException();
        }
    }

    public static boolean isSTDIO(int fileno) {
        if (fileno >= 0 && fileno <= 2) {
            return true;
        }

        return false;
    }

    public boolean isJVMDefault(Object stream) {
        switch (this) {
            case IN:  return stream == System.in;
            case OUT: return stream == System.out;
            case ERR: return stream == System.err;
            default:  return false;
        }
    }
}