EventBus/src/org/greenrobot/eventbus/EventBusBuilder.java
public EventBus installDefaultEventBus() {
        synchronized (EventBus.class) {
            if (EventBus.defaultInstance != null) {
                throw new EventBusException("Default instance already exists." +
                        " It may be only set once before it's used the first time to ensure consistent behavior.");
            }
            EventBus.defaultInstance = build();
            return EventBus.defaultInstance;
        }
    }
public EventBus installDefaultEventBus() {
        synchronized (EventBus.class) {
            if (EventBus.defaultInstance != null) {
                throw new EventBusException("Default instance already exists." +
                        " It may be only set once before it's used the first time to ensure consistent behavior.");
            }
            EventBus.defaultInstance = build();
            return EventBus.defaultInstance;
        }
    }
public EventBus installDefaultEventBus ( ) { synchronized ( EventBus . class ) { if ( EventBus . defaultInstance != null ) { throw new EventBusException ( "Default instance already exists." + " It may be only set once before it's used the first time to ensure consistent behavior." ) ; } EventBus . defaultInstance = build ( ) ; return EventBus . defaultInstance ; } }
Installs the default EventBus returned by {@link EventBus#getDefault()} using this builders' values. Must be
done only once before the first usage of the default EventBus.

@throws EventBusException if there's already a default EventBus instance in place
Installs the default EventBus returned by { @link EventBus#getDefault () } using this builders values . Must be done only once before the first usage of the default EventBus .