test

String test="old data";
        final Observable observable=Observable.just(test);
        Observable observable_defer =  Observable.defer(new Callable<ObservableSource<String>>() {
            @Override
            public ObservableSource<String> call() throws Exception {
                return observable;
            }
        });
        test="new data";
        observable.subscribe(consumer2);//打印  old data
        observable_defer.subscribe(consumer2);//打印  new data

//數據發射源對象
ObservableEmitter   observableEmitter   ;
private void sendData(){
if(observableEmitter   != null){
    for(int i = 0;i < 10; i++){
        //數據發射源對象發射數據
         observableEmitter .onNext("Observable  數據data " +i);
   }
   observableEmitter .onComplete();
}
}
 private ObservableOnSubscribe<String> observableOnSubscribe = new      ObservableOnSubscribe<String>() {
        @Override
        public void subscribe(@NonNull ObservableEmitter<String> e) throws Exception {
            printThread("subscribe");
            observableEmitter   = e; 
            observableEmitter .onNext("Observable  數據data");
            sendData();
        }
    };
Observable observable = Observable.create(observableOnSubscribe )