title: Raspberry pi flashing LED issue - Python vs Java
body: <p>i am trying to make an LED light flash on the raspberry pi using some code i found online ( i know - not the best but it was a tutorial site)</p>
  
  <p>When i run the following python code the led light flashes;</p>
  
  <pre><code>import RPi.GPIO as GPIO
  import time
  pinNum = 4
  GPIO.setmode(GPIO.BCM) #numbering scheme that corresponds to breakout board and pin layout
  GPIO.setup(pinNum,GPIO.OUT) #replace pinNum with whatever pin you used, this sets up that pin as an output
  #set LED to flash forever
  while True:
    GPIO.output(pinNum,GPIO.HIGH)
    time.sleep(0.5)
    GPIO.output(pinNum,GPIO.LOW)
    time.sleep(0.5)
  </code></pre>
  
  <p>When i run the following Java code which is supposed to do the same - all i get to the console are the print statements which i have added - no flashing light</p>
  
  <pre><code>import com.pi4j.io.gpio.GpioController;  
   import com.pi4j.io.gpio.GpioFactory;  
   import com.pi4j.io.gpio.GpioPinDigitalOutput;  
   import com.pi4j.io.gpio.PinState;  
   import com.pi4j.io.gpio.RaspiPin;  
  
   public class ControlGpioExample {  
    public static void main(String[] args) throws InterruptedException {  
       final GpioController gpio = GpioFactory.getInstance();  
       final GpioPinDigitalOutput ledPin = gpio.provisionDigitalOutputPin(RaspiPin
  .GPIO_04, "MyLED", PinState.LOW);  
       System.out.println("Started");
       try  
       {  
         while(true)  
         {
           System.out.println(ledPin==null);
           System.out.println("Looping pin now"); 
           ledPin.high();
           System.out.println("Set high called");  
           Thread.sleep(2000);  
           ledPin.low();  
           System.out.println("Set low called");
           Thread.sleep(2000);  
         }  
       }  
       catch(Exception ex)  
       {  
         gpio.shutdown();  
         ex.printStackTrace();  
       }  
     }  
   }  
  </code></pre>
  
  <p>Does anyone know why this might be? I think logically the should be doing the same thing - both are using the same GPIO pin number from the pi too</p>
  
  <p>Thanks for your help</p>