Clearing an ArrayList

Processing Libraries
5

hi chisir
i>=0 doesn’t clear the array, just deactivates it. when turned on again, it continues from where it stopped.

using r.rings.clear() it returns

Sep 20, 2018 1:24:32 PM controlP5.ControlBroadcaster printMethodError
SEVERE: An error occured while forwarding a Controller event, please check your code at ringToggle
java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at controlP5.ControlBroadcaster.invokeMethod(Unknown Source)
	at controlP5.ControlBroadcaster.callTarget(Unknown Source)
	at controlP5.ControlBroadcaster.broadcast(Unknown Source)
	at controlP5.Controller.broadcast(Unknown Source)
	at controlP5.Toggle.setState(Unknown Source)
	at controlP5.Toggle.setValue(Unknown Source)
	at controlP5.Toggle.setValue(Unknown Source)
	at dome_004$ControlFrame.setup(dome_004.java:356)
	at processing.core.PApplet.handleDraw(PApplet.java:2404)
	at processing.awt.PSurfaceAWT$12.callDraw(PSurfaceAWT.java:1557)
	at processing.core.PSurfaceNone$AnimationThread.run(PSurfaceNone.java:313)
Caused by: java.lang.NullPointerException
	at dome_004$ControlFrame.ringToggle(dome_004.java:467)
	... 15 more

using, erasing one by one

for (int i=0; i<r.rings.size(); i++) {
        Ring ri=r.rings.get(i);
        r.rings.remove(i);
      }

returns

Sep 20, 2018 1:27:21 PM controlP5.ControlBroadcaster printMethodError
SEVERE: An error occured while forwarding a Controller event, please check your code at ringToggle
java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at controlP5.ControlBroadcaster.invokeMethod(Unknown Source)
	at controlP5.ControlBroadcaster.callTarget(Unknown Source)
	at controlP5.ControlBroadcaster.broadcast(Unknown Source)
	at controlP5.Controller.broadcast(Unknown Source)
	at controlP5.Toggle.setState(Unknown Source)
	at controlP5.Toggle.setValue(Unknown Source)
	at controlP5.Toggle.setValue(Unknown Source)
	at dome_004$ControlFrame.setup(dome_004.java:356)
	at processing.core.PApplet.handleDraw(PApplet.java:2404)
	at processing.awt.PSurfaceAWT$12.callDraw(PSurfaceAWT.java:1557)
	at processing.core.PSurfaceNone$AnimationThread.run(PSurfaceNone.java:313)
Caused by: java.lang.NullPointerException
	at dome_004$ControlFrame.ringToggle(dome_004.java:468)
	... 15 more