how to print logs in cmd console while execute android instrument test

I open a cmd on windows system, and then input "adb shell am instrument -w http://ift.tt/1Tz0pXd" to run android test. I want to print log in the cmd while run the test, can anyone tell me how to write code to print log? I have tied system.out.println("xx") and Log.i("xx","xx"), but it's useless.