Viewing stdout and stderr
By default, the Android system sends stdout and stderr (System.out and System.err) output to /dev/null. In processes that run the Dalvik VM, you can have the system write a copy of the output to the log file. In this case, the system writes the messages to the log using the log tags stdout and stderr, both with priority I.
To route the output in this way, you stop a running emulator/device instance and then use the shell command setprop to enable the redirection of output. Here’s how you do it:
$ adb shell stop
$ adb shell setprop log.redirect-stdio true
$ adb shell start
The system retains this setting until you terminate the emulator/device instance. To use the setting as a default on the emulator/device instance, you can add an entry to /data/local.prop on the device.
Original Source: Android Developer page