blueflood-core/src/main/java/com/rackspacecloud/blueflood/eventemitter/Emitter.java
public Emitter once(final String event, final Listener<T> fn) {
        Listener on = new Listener<T>() {
            @Override
            public void call(T... args) {
                Emitter.this.off(event, this);
                fn.call(args);
            }
        };

        this.onceCallbacks.put(fn, on);
        this.on(event, on);
        return this;
    }
public Emitter once(final String event, final Listener<T> fn) {
        Listener on = new Listener<T>() {
            @Override
            public void call(T... args) {
                Emitter.this.off(event, this);
                fn.call(args);
            }
        };

        this.onceCallbacks.put(fn, on);
        this.on(event, on);
        return this;
    }
public Emitter once ( final String event , final Listener < T > fn ) { Listener on = new Listener < T > ( ) { @ Override public void call ( T ... args ) { Emitter . this . off ( event , this ) ; fn . call ( args ) ; } } ; this . onceCallbacks . put ( fn , on ) ; this . on ( event , on ) ; return this ; }
Adds a one time listener for the event.

@param event an event name.
@param fn
@return a reference to this object.
Adds a one time listener for the event .