/guava/guava/src/com/google/common/util/concurrent/AbstractExecutionThreadService.java
delegate.addListener( executor) ;
delegate.addListener ( listener, executor ) ;
@Override public final State state() { return delegate.state(); } @Override public final void addListener(Listener listener, Executor executor) { <extra_id_0> } @Override public final Throwable failureCause() { return delegate.failureCause(); } @CanIgnoreReturnValue