reading-transactions.md

Reading transactions

Now that you have the means to represent a transaction as an object in your code, it's a good time to write the code that will read the transactions from the data file.

Another class

It's good practice in Java to write small classes that have only one or two responsibilities each. Reading a CSV file and producing a list of transactions is a good candidate for a job that belongs in its own class.

Go ahead and create another class - call it anything you like, as long as its name makes sense in the context of what its job is.

Breaking into methods

The way I see it, this class needs to be able to do two things: it needs to be able to read the lines from the data file, and it needs to be able to turn each line into a Transaction object before returning it.

That makes the following method structure promising for this class:

public static List<Transaction> getTransactionsFromFile(String filename) {
    // ...
}

private static Transaction convertLineToTransaction(String line) {
    // ...
}

You should fill in the currently-blank implementations of these methods so that they behave as described. Some hints: to read the lines from a file, Files.readAllLines will be helpful, and to convert a single line to a transaction you will probably want to make use of String::split.

You can check that your code is working by temporarily putting something in your main method that calls it, and either having it print out the details of the transactions or setting a breakpoint and examining the transactions in the debugger.

Once you're happy with it, take a look at how we'll want to be Storing Transactions.