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public final class EntitiesInterpolate extends Command<StateEntities> {
        private final float alpha;
        public EntitiesInterpolate(final float alpha) {
                super(StateEntities.class);
                this.alpha = alpha;
        }
        @Override
        public void execute(StateEntities listener) {
                listener.interpolate(alpha);
        }
}

//Nope
currentState.execute(new EntitiesInterpolate(accumulatedTime / SECONDS_PER_FRAME));


public final void execute(Command<StateComponent> command) {
        if (hasComponent(command.getListeningClass())) {
                for (StateComponent component : components) {
                        if (command.getListeningClass().isInstance(component)) {
                                command.execute(component);
                        }
                }
        }
}


public final class StateEntities extends StateComponent {}