Profile a block in JRuby

prof.rb

# Remember to pass `--profile.api` to JRuby:
#   jruby --profile.api prof.rb

require "jruby/profiler"

def main
  prof = JRuby::Profiler.profile do
    puts(f1)
    puts(f2)
  end

  save_prof(prof)
end

def f1
  sleep(1)
  "f1 done"
end

def f2
  x = 0
  t0 = Time.now
  
  while
    x = x + 1
    t = Time.now - t0
    break if t > 1.0
  end

  "f2 done in #{t}"
end

def save_prof(prof)
  f = java.io.File.new("profile.api.html")
  pstream = java.io.PrintStream.new(f)
  printer = JRuby::Profiler::HtmlProfilePrinter.new(prof)
  printer.printHeader(pstream)
  printer.printProfile(pstream)
  printer.printFooter(pstream)
ensure
  pstream.close
end

main