This time we look at functions.
Let’s take a simple function from Java:
public int mult(int num1, int num2){
return num1 * num2;
}
In Kotlin it would look like this: Continue reading “Learning Kotlin – Part 6”
Learning Kotlin – Part 5
This time we deal with loops
Loops
Kotlin has two types of loops: for and while.
For-loop
for(x in 1..10){
println("Loop: $x")
}
While-loop
var i = 10
while(i > 0) {
println("$i")
i--
}
Break & Continue
for(x in 1..20){
if(x % 2 == 0){
continue
}
println("Odd: $x")
if(x == 15) break
}
Iterate over collections
val myArray: Array<Int> = arrayOf(3,6,9)
for(i in myArray.indices){
println("Mult3 : ${myArray[i]}")
}
Enumerate-like iteration over collections
When you are familiar with Python’s enumerate fucntion You will appreciate the withIndex-function:
for((index, value) in myArray.withIndex()){
println("Index : $index Value : $value")
}
Learning Kotlin – Part 4
Conditionals
This is a pretty quick one:
Kotlin has the standard Java if / else if / else statements Continue reading “Learning Kotlin – Part 4”
Learning Kotlin – Part 3
After Learning Kotlin – Part 1 and Learning Kotlin – Part 2 we will now dive into the ranges.
One nice little feature is the .. syntax: you can generate an IntRange object just by specifying the start and the end element:
val oneTo10 = 1..10
Internet access in Android
If You want to access some internet resouces from your Android app you add
<uses-permission android:name="android.permission.INTERNET"/> <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
to your AndroidManifest.xml
When You have resources which do not use TLS (https but just http) you have to add
<application
...
android:usesCleartextTraffic="true">
</application>
Learning Kotlin – Part 2
In Learning Kotlin – Part 1 we looked at some basic concepts like type inference and string handling. In this part we deal with arrays:
You can easily create an array with the arrayOf function
var myArray = arrayOf(1, 1.23, "Jörn")
Element access
Learning Kotlin – Part 1
Motivation
I wanted to try writing an Android app. In spite of using plain old Java I wanted to give the new kid on the block Kotlin (from the Jetbrains folks) a try.
First observations
Coming from a Python background it’s good to see that Kotlin doesn’t use semi-colons! But the curly braces from Java make code blocks are still there, hmpf… Continue reading “Learning Kotlin – Part 1”
The 10-3-2-1-0 Rule
10h before sleep – no caffeine
3h before sleep – no more eating
2h before sleep – no more work
1h before sleep – no more tv / tablet
0 times snoozing the alarm clock in the morning
So when I want to get to bed at around 22:00 (10pm) my schedule would look like the following
- 12:00 – stop drinking caffee
- 19:00 – stop eating
- 20:00 – stop working
- 21:00 – stop watching Netflix/Prime/Youtube
- Stop snoozing the alarm clock when it rings at 6:00
After one week my experience is this:
- 12:00 – stop drinking caffee
- good and easy to do, I drink one cup in the morning and at max 2 cups at work
- positive effect on my skin picking issue
- 19:00 – stop eating
- not as easy, sometimes I’m late from work
- 20:00 – stop working
- no-brainer, I rarely stay at work after 19:00
- 21:00 – stop watching Netflix/Prime/Youtube
- hard, hard, hard, at the moment I practice guitar / piano from around 19:30 till 21:00
- Stop snoozing the alarm clock when it rings at 6:00
- not working I still snooze between 2 to 5 times, so I get up at 6:30 minimum
Some tweeking
I shifted my sleep time from 22:00 – 6:00 to 22:30 – 6:30
- 12:30 – stop drinking coffee
- 19:30 – stop eating
- 20:30 – stop working
- 21:30 – stop watching Netflix/Prime/YouTube
- Stop snoozing the alarm clock when it rings at 6:30
SQL-Basics: Relations
As the Junior Data Scientist of Knight Industries we created a table to keep track of all our operatives: SQL-Basics: Create, Read, Update, Delete
Devon asks us to keep track of our operations aka missions as well. For the first implementation let us assume that a mission has one operative and an operative can participate in multiple missions. that’s what we call an 1 to many relationship.
+------------+ +----------+ | |1 active in n| | | operative +-----------------+ missions | | | | | +------------+ +----------+
Missions have an id, a code name like “Phantom Liberty”, an operative id and a total cost. Continue reading “SQL-Basics: Relations”
SQL-Functions
In SQL-Basics
we learned the standard SQL statements to create a table, insert data into it, retrieving data from tables and altering data. Now we want to do even
Devon is a data driven man and to evaluate our mission, he likes to know from us:
-
- how many missions we finished
- the total cost of all missions
- the mission with the lowest cost
- the mission with the highest cost
- the average mission cost
- the five most expensive missions
SELECT COUNT(*) FROM missions;
SELECT SUM(total_cost) FROM missions; SELECT MIN(total_cost) FROM missions; SELECT MAX(total_cost) FROM missions; SELECT AVG(total_cost) FROM missions; SELECT * FROM missions ORDER BY total_cost DESC LIMIT 5;