1. Wrong way to use it
Runtime.getRuntime().exec("xxx");
2. Correct usage
//You need to specify parameter one: command location; parameter two: -c means execute the first parameter first; parameter three: your command.
Runtime.getRuntime().exec(new String[]{"/bin/sh","-c","xxx"});
Such as:
try {
Runtime.getRuntime().exec(new String[]{"/system/bin/sh","-c","reboot"});
}catch (Exception e) {
e.printStackTrace();
}