FileWriter | .NET project for writing files to local or remote hosts | Privacy library

Handle the exception while writing fw.write(x + "ms"); to file see below code . FileWriter write function thow IO exception which you didn't handle.

Try using either:

Synchronization will only work if done on the same actual object. Your second version will not work because it creates a new object, and therefore a new lock. What you would need is a registry of locks. A small example, using not synchronized but ReentrantLock:

When I copy-paste your code, I cannot reproduce it.

This is the test grammar:

You have identified the issue correctly, in your WriteToFile method you are only adding a single book from your bookTitles list to the file, more precisely you are only adding the first book that was input in the current run.

You would have to change that code into a loop that iterates over the whole bookTitles list. Since you save all the data sequentially into the List, and since you know that you have exactly 4 units of data per book, you can use a for loop with an index increment of 4. Then instead of accessing indices at 0, 1, 2, 3 you access indices at i, i+1, i+2, i+3 inside the loop.

Since the index increment is 4 this means that the indices in your loop iterations will be the following:

Try the below code :

I just want to start by saying that there are many ways to do this, and what's considered the "best" approach is highly dependent on the specifics to your use case (and sometimes personal preferences).

The most important thing to remember is that the watch has very limited resources (battery, memory, CPU) compared to a typical phone.

Here are a few things to keep in mind no matter what your exact solution will look like:

1. Writing to a file is an expensive operation. Doing this for every data point you receive from a sensor is not ideal. Consider saving your data to a database using Room instead. An easier alternative, as long as you are OK potentially losing some data if the app crashes or the device reboots unexpectedly, is to keep it in memory. This can be done using a basic array or some sort of Map (timestamp and value) depending on exactly what data you need. You can also use a hybrid of the two approaches and save data in batches.

2. Sending data between the watch and the phone is also expensive. I highly suggest storing things on the watch itself and transfer it to the phone only when needed. This can be a manual trigger, daily at a certain time, when the watch is charging, or some other clever strategy to minimize the impact on the watch's battery life.

3. You can send your data to the phone using the Wearable Data Layer API. You will have to set up either a MessageClient or a ChannelClient depending on how much data you need to transfer. If you stick to data structures that are supported by Android (as opposed to creating your own one), sending them over should be fairly straight forward.

4. If you need to process or format your data in order for it to be easily analyzed in MATLAB, consider doing this on the phone rather than the watch. Simpler operations on reasonably sized data sets can of course be performed directly on the watch.

Exactly how you decide to get the file to your computer is outside of the scope of what I'm trying to answer here. There are plenty of well-documented ways to do this. The easiest being to manually transfer it via adb. This can be done directly from the watch too, so you don't even have to send data to the phone.

Out of memory is coming if the whole file is read as a string in memory. What if file is read chunk by chunk and do your operations and then write that chunk with modified data to another file, Hence saving the out of memory error.

You can try using buffered reader to read chunk by chunk :

For the first question when the file is opened for writing (as it is when you create the FileWriter) it is cleared, the length is set to 0. If you want to append you need to open the file for appending. There is a constructor with a boolean append flag you can use for that.

For the second question getClass().getResource("/Test.txt") refers to the compiled resources typically found in target/classes or bin. If you delete the file from src/resources it will not be built and there is no file in the target directory. It won't help that you create the file in src when you run the program; by then it is too late. The resource is not found and you get a NullPointerException.