I tried to understand the logic behind inputstreams and reading from files, but I fail to understand how you can read from a file using an inputstream.
My understanding is that when using input devices like a keyboard, you send input data through the input stream to the system. If you are reading from an input stream, aren't you reading the input data that's being send to the system at that time?
If we are creating an inputstream with the following code:
FileInputStream test = new FileInputStream("loremipsum.txt");
And if we try to read from the newly created inputstream with test.read(); how is there any data flowing through the inputstream? As no inputdata has been input from an input device at the time, but has already been input way beforehand. Is there something I'm missing out on? It almost seems to me as input streams are used in two different ways: Java using inputstreams to read data from a source and input devices using to input data to a source.
Java streams are a general concept / interface - a stream of data that you need to open, then read the data from (or write data to for output streams), then close. The basic stream only supports sequential reading / writing, no random access. Also, the data may or may not be readily available when you attempt to read from the stream, so the read may or may not block.
This abstraction allows us to use the same approach regardless of where we read the data from - it might be keyboard, a file, a network connection, output form another program or even some kind of generator that generates an endless sequence of data. Simply put, reading the input from file behaves the same as if someone in the background opened the file and typed its content on the keyboard really fast.
There are ways in Java to read the file in another ways (e.g. random access instead of sequential), but if you need to read the file from start to end, streams are a useful abstraction.