How I came to write the Scala Cookbook alvin June 22, 2017 - 10:24am

The funny thing about writing the Scala Cookbook is that it started as a whim. I was just about to leave for a vacation at the beach, and right before I turned off the computer, a thought flashed in my mind, “I should contact the people at O’Reilly about writing a cookbook for Scala.” I then had a doubt that they would actually do it, but I applied the “What the heck” rule — i.e., “What the heck, what do I have to lose?” — and sent the email.

I dug around the internet for a few minutes, found the correct O’Reilly email address, sent them a message, turned off the computer, and drove to the beach. While I was at the beach the publisher wrote and said, “Love it, send me a full proposal!”

So if you’re thinking about doing something, but are afraid or uncertain about doing it ... apply the “What the heck” rule, and give it a shot. :)

Scala: How to read input from one file while writing output to another file alvin June 14, 2017 - 3:53pm

Without much introduction or discussion, here’s a Scala example that shows how to read from one text file while simultaneously writing the uppercase version of the text to a second output file:

I can't write a book

As shown in the image, I’ve finally come to the realization that I can’t write a book. But I can write a few sentences, and then a few pages, and eventually a chapter on a given topic. And then I can write another chapter, and then another. But to sit down and say, “I’m going to write a book,” no, that’s too hard.

How to read and write binary files in Scala

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 12.3, “How to read and write binary files in Scala.”


You want to read data from a binary file or write data to a binary file.


Scala doesn’t offer any special conveniences for reading or writing binary files, so use the Java FileInputStream and FileOutputStream classes.

How to write text files in Scala

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 12.2, “How to write text files in Scala.”


You want to write plain text to a file, such as a simple configuration file, text data file, or other plain-text document.


Scala doesn’t offer any special file writing capability, so fall back and use the Java PrintWriter or FileWriter approaches:

Android: Generic methods to write/save Android preferences data

I was working with Android Preferences recently, and after writing a few “save my preference” methods, I decided to take a few minutes to organize my code and put all of those Preference methods in a PreferenceUtils class. I made the methods static, and following functional programming principles, I made their output depend only on their input, so they require you to pass in a Context reference, along with your preference key and value.

How to read and write from a file in a Linux bash shell script

I’m currently writing a complicated Linux bash shell script where I need to keep a counter in an external file, and to do so, I need to be able to write to a file and then read from that file.

In short, this is how I write my counter to that file:

# create a variable to represent the filename

# write to the file
echo "0" > $COUNTER_FILE

Later in the code I increment the counter and write it to the file like this:

Scala: Saving/writing XML to a file

Problem: You want to write XML data to a file in a Scala application, such as saving application data or configuration information to a file.


Use the scala.xml.XML.save method to write a Scala literal to a file. Given this XML literal: