Java将异步调用转换为同步调用

调用外部的Api时，根据自己业务需求有时需要同步调用，如果这些Api没有提供同步调用的方法，此时该如何转同步调用呢

下面提供一种Java中的实现方式：

public class AsyncCallback {
    private Boolean finished = null;

    public AsyncCallback call() {
        new Thread() {
            @Override
            public void run() {
                synchronized (AsyncCallback.this) {
                    try {
                        Thread.sleep(3000);

                        finished = true;
                    } catch (InterruptedException ignore) {
                        finished = false;
                    }
                    AsyncCallback.this.notifyAll();
                }
            }
        }.start();

        return this;
    }

    public boolean isFinished() {
        synchronized (this) {
            while (finished == null) {
                try {
                    wait();
                } catch (InterruptedException ignore) {
                }
            }
        }

        return finished;
    }

    public static Observable<Boolean> asyncCall() {
        return Observable.defer(new Callable<ObservableSource<? extends Boolean>>() {
            @Override
            public ObservableSource<? extends Boolean> call() throws Exception {
                return Observable.just(new AsyncCallback().call().isFinished());
            }
        });
    }

    @SuppressLint("CheckResult")
    public static void testAsync2Sync() {
        asyncCall().subscribeOn(Schedulers.computation())
                .observeOn(AndroidSchedulers.mainThread())
                .doOnSubscribe(new Consumer<Disposable>() {
                    @Override
                    public void accept(Disposable disposable) throws Exception {
                        Log.e("HTTP-LOG", "start call sync method");
                    }
                })
                .subscribe(new Consumer<Boolean>() {
                    @Override
                    public void accept(Boolean aBoolean) throws Exception {
                        Log.e("HTTP-LOG", "sync call returned, " + aBoolean);
                    }
                });
    }

通过这样的转换，就可以将异步接口转换为同步调用