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LESSON 2 OF 414 · WELCOME TO SCALA

Introduction to Strings in Scala: Text in Double Quotes

Lesson Read the full explanation

TL ; DR:

  • To create a string in Scala, we put some text inside Double quotes ("Hello world").


  • Be careful not to forget any quote! This code missing a " at the end:

    println("Welcome!)

    would make the compiler report the error unclosed string literal


Full lesson:

How boring would our life as humans be if we communicated only using numbers? Luckily we have letters, words and languages to express what we think!

We can also use letters and words in Scala to express more meaningful messages like we do in real life.

Strings:

In programming, a string is any block of text e.g. any sequence of characters from your keyboard (letters, numbers, spaces, symbols, etc.).

To create a string in Scala, we put some text inside Double quotes like this "Hello world".

For example, we can use strings inside the println() function for printing messages to the console:

println("My name is Andy")
println("Welcome to AlgoCademy!")

The output of this code is:

My name is Andy
Welcome to AlgoCademy!

As you can see, the quotes are not printed. That's because quotes are not part of the string. Their job is solely to let Scala know when a string declaration starts and when it ends.

Assignment
Follow the Coding Tutorial and let's work with strings!

Hint
Look at the examples above if you get stuck.

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    SCALA · WELCOME TO SCALA

    Introduction To Strings in Scala, explained

    What a string is

    A string is a piece of text: any sequence of characters you can type, including letters, digits, spaces and symbols. Programs use strings for names, messages and anything else that is words rather than numbers. In Scala the type is called String.

    Writing a string

    To write a string, put the text between double quotes:

    println("My name is Andy")
println("Welcome to the course")

    The output is:

    My name is Andy
Welcome to the course

    The quotes are not printed. They are not part of the string; their only job is to tell Scala where the text starts and where it ends. Everything between them, spaces included, is part of the string.

    Double quotes only

    Scala uses double quotes for strings. Single quotes mean something else: 'a' is a Char, a single character, and a single-quoted piece of text with several characters is an error. When you want a string, even a one-character one, use double quotes.

    Strings versus numbers

    The quotes change what a value is. 12 is a number you can do arithmetic with. "12" is two characters of text. With +, a number adds and a string joins:

    println(12 + 1)
println("12" + 1)

    13
121

    In the second line the number is turned into text and attached to the end of the string. Subtraction is different: "12" - 1 doesn't compile, because a String has no - method.

    Joining and measuring strings

    The + operator joins two strings into a new one, and the length member tells you how many characters a string holds, spaces included:

    println("Hello" + " " + "world")
println("Andy".length)

    Hello world
4

    A string can also be empty, written "". It has length 0 and prints as an empty line.

    The most common mistake: a missing quote

    Every string needs both of its quotes. This line is missing the closing one:

    println("Welcome!)

    Scala can't tell where the text ends, so it stops with the compile error unclosed string literal and the program does not run. The fix is to add the quote before the closing parenthesis:

    println("Welcome!")

    Matching pairs matter in general. Whenever you open a quote or a parenthesis, make sure there is something to close it.

    Quotes inside a string

    To put a double quote inside a string, write a backslash before it:

    println("She said \"hi\"")

    She said "hi"

    The backslash tells Scala that this quote is part of the text and not the end of the string.

    The exercise

    The task is to print the text I love coding!. Put the text in double quotes and pass it to println:

    println("I love coding!")

    The console shows I love coding!, without the quotes. The text must match exactly, including the capital I and the exclamation mark at the end.

    Key takeaways

    • A string is text written between double quotes.
    • The quotes mark the start and end of the string and are not printed.
    • 12 is a number and "12" is a string; + adds the first and joins the second.
    • A missing closing quote gives an unclosed string literal error.
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