一、reduce语法

  public Observable<Integer> getRxJavaCreateExampleData() {
        return Observable.create(new ObservableOnSubscribe<Integer>() {
            @Override
            public void subscribe(ObservableEmitter<Integer> emitter) throws Exception {
                LogUtils.debug(TAG, "getRxJavaCreateExampleData---:" + Thread.currentThread().getName() + "--:" + 1);
                emitter.onNext(1);

                LogUtils.debug(TAG, "getRxJavaCreateExampleData---:" + Thread.currentThread().getName() + "--:" + 2);
                emitter.onNext(2);
//                Thread.sleep(5000);
                LogUtils.debug(TAG, "getRxJavaCreateExampleData---:" + Thread.currentThread().getName() + "--:" + 3);
                emitter.onNext(3);
                emitter.onComplete();
                LogUtils.debug(TAG, "getRxJavaCreateExampleData---:" + Thread.currentThread().getName() + "--:" + 4);
                emitter.onNext(4);

            }
        });
    }
  public void rxJavaReduceExample() {
        Disposable disposable = model.getRxJavaCreateExampleData()
                .subscribeOn(Schedulers.io())
                .unsubscribeOn(Schedulers.io())
                .reduce(new BiFunction<Integer, Integer, Integer>() {
                    @Override
                    public Integer apply(Integer integer, Integer integer2) throws Exception {
                        LogUtils.error(TAG, "rxJavaReduceExample--:" + Thread.currentThread().getName() + "-consumer-:" + integer+"---"+integer2);
                        return integer+integer2;
                    }
                }).observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Consumer<Integer>() {
                    @Override
                    public void accept(Integer integer) throws Exception {
                        LogUtils.error(TAG, "rxJavaReduceExample--:" + Thread.currentThread().getName() + "-consumer-:" + integer);
                    }
                });
        compositeDisposable.add(disposable);
    }

日志

08-19 15:11:38.636 12439-12483/com.example.zhang E/MainPresenter: rxJavaReduceExample--:RxCachedThreadScheduler-1-reduce-:1---2
    rxJavaReduceExample--:RxCachedThreadScheduler-1-reduce-:3---3
08-19 15:11:38.641 12439-12439/com.example.zhang E/MainPresenter: rxJavaReduceExample--:main-consumer-:6

二、reduce方法2

    public void rxJavaReduceExample() {
        Disposable disposable = model.getRxJavaCreateExampleData()
                .subscribeOn(Schedulers.io())
                .unsubscribeOn(Schedulers.io())
                .reduce(10, new BiFunction<Integer, Integer, Integer>() {
                    @Override
                    public Integer apply(Integer integer, Integer integer2) throws Exception {
                        LogUtils.error(TAG, "rxJavaReduceExample--:" + Thread.currentThread().getName() + "-reduce-:" + integer + "---" + integer2);
                        return integer + integer2;
                    }
                }).observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Consumer<Integer>() {
                    @Override
                    public void accept(Integer integer) throws Exception {
                        LogUtils.error(TAG, "rxJavaReduceExample--:" + Thread.currentThread().getName() + "-consumer-:" + integer);
                    }
                });
        compositeDisposable.add(disposable);
    }

日志

08-19 15:08:37.078 12228-12282/com.example.zhang E/MainPresenter: rxJavaReduceExample--:RxCachedThreadScheduler-1-reduce-:10---1
    rxJavaReduceExample--:RxCachedThreadScheduler-1-reduce-:11---2
    rxJavaReduceExample--:RxCachedThreadScheduler-1-reduce-:13---3
08-19 15:08:37.084 12228-12228/com.example.zhang E/MainPresenter: rxJavaReduceExample--:main-consumer-:16

总结

1、reduce(BiFunction<T, T, T> reducer) 把接受到的数据叠加起来，返回一个结果
2、reduce(R seed, BiFunction<R, ? super T, R> reducer) seed初始值