Multiline strings with trimIndent in Kotlin - Step-by-Step Execution

Concept Flow - Multiline strings with trimIndent

Start multiline string with triple quotes

↓

Write string lines with indentation

↓

Call trimIndent()

↓

Remove common leading whitespace

↓

Return trimmed string

↓

Use or print the string

The flow shows how Kotlin reads a multiline string, removes common indentation with trimIndent(), and returns the cleaned string.

Execution Sample

Kotlin

val text = """
    Hello,
      Kotlin!
""".trimIndent()
println(text)

This code creates a multiline string with indentation, removes common leading spaces using trimIndent(), and prints the cleaned string.

Execution Table

Step	Action	String Content	Indentation Removed	Resulting String
1	Start multiline string	" Hello,\n Kotlin!"	N/A	" Hello,\n Kotlin!"
2	Apply trimIndent()	Same as above	4 spaces (common indent)	"Hello,\n Kotlin!"
3	Print string	N/A	N/A	Hello, Kotlin!

💡 All common leading spaces removed, string printed without extra indentation.

Variable Tracker

Variable	Start	After trimIndent()	Final
text	" Hello,\n Kotlin!"	"Hello,\n Kotlin!"	"Hello,\n Kotlin!"

Key Moments - 2 Insights

Why does trimIndent() remove only 4 spaces and not all spaces from each line?

trimIndent() removes the smallest common indentation from all lines, so it only removes 4 spaces because that is the minimum indentation shared by all lines (see execution_table step 2).

What happens to lines that have more indentation than the common minimum?

Lines with more indentation keep their extra spaces after trimIndent(), preserving relative indentation (see ' Kotlin!' line in execution_table step 2).

Visual Quiz - 3 Questions

Look at the execution_table step 2, how many spaces are removed by trimIndent()?

A All spaces

B 4 spaces

C 2 spaces

D No spaces

💡 Hint

Check the 'Indentation Removed' column in execution_table step 2.

At which step is the string actually printed to the console?

A Step 3

B Step 2

C Step 1

D After all steps

💡 Hint

Look at the 'Action' column for when printing happens in execution_table.

If the first line had no indentation, what would trimIndent() remove?

A 4 spaces from all lines

B All leading spaces from all lines

C No spaces, because common indent is zero

D Only spaces from the first line

💡 Hint

Recall trimIndent() removes the smallest common indent shared by all lines.

Concept Snapshot

Multiline strings use triple quotes """ to include line breaks and spaces.
trimIndent() removes the smallest common leading spaces from all lines.
This keeps relative indentation but cleans up extra spaces.
Use trimIndent() to avoid unwanted indentation in multiline strings.
Print the string to see the cleaned result.

Full Transcript

This example shows how Kotlin handles multiline strings with triple quotes. The string includes lines with indentation. When trimIndent() is called, it finds the smallest number of spaces common to all lines and removes that from each line. This keeps the relative indentation intact but removes extra leading spaces. Finally, printing the string shows the cleaned text without unwanted indentation. This helps keep code readable while formatting strings nicely.

Practice

1. What does the trimIndent() function do when used with multiline strings in Kotlin?

easy

A. It converts the string to uppercase.

B. It adds extra spaces at the beginning of each line.

C. It splits the string into a list of lines.

D. It removes the common leading whitespace from each line.

Solution

1. Step 1: Understand the purpose of trimIndent()

   The function trimIndent() removes the common leading whitespace from every line in a multiline string.

2. Step 2: Effect on multiline strings

   This makes the string output aligned neatly without extra indentation caused by code formatting.

3. Final Answer:

   It removes the common leading whitespace from each line. -> Option D

4. Quick Check:

   trimIndent() = removes leading spaces [OK]

Hint: trimIndent() cleans leading spaces for neat multiline strings [OK]

Common Mistakes:

• Thinking trimIndent() adds spaces instead of removing
• Confusing trimIndent() with uppercase conversion
• Assuming trimIndent() splits strings into lines

2. Which of the following is the correct syntax to create a multiline string with trimmed indentation in Kotlin?

easy

A. val text = """Hello\nWorld""".trimIndent()

B. val text = "Hello\nWorld".trimIndent()

C. val text = '''Hello\nWorld'''.trimIndent()

D. val text = ""Hello\nWorld"".trimIndent()

Solution

1. Step 1: Identify multiline string syntax

   Kotlin uses triple double quotes """ to create multiline strings.

2. Step 2: Apply trimIndent() correctly

   Calling trimIndent() on the multiline string removes common leading spaces.

3. Final Answer:

   val text = """Hello\nWorld""".trimIndent() -> Option A

4. Quick Check:

   Triple quotes + trimIndent() = correct syntax [OK]

Hint: Use triple quotes """ for multiline strings with trimIndent() [OK]

Common Mistakes:

• Using single quotes instead of triple quotes
• Trying to trimIndent() on a normal string
• Wrong quote count causing syntax errors

3. What will be the output of the following Kotlin code?

val text = """
    Kotlin
    is
    fun
""".trimIndent()
println(text)

medium

A. Kotlin
is
fun

B. Kotlin
is
fun

C. Kotlin
is
fun

D. Kotlin is fun

Solution

1. Step 1: Analyze the multiline string with indentation

   The string has 4 spaces before each line inside the triple quotes.

2. Step 2: Effect of trimIndent()

   trimIndent() removes the common 4-space indentation from all lines.

3. Final Answer:

   Kotlin is fun -> Option C

4. Quick Check:

   trimIndent() removes leading spaces = clean lines [OK]

Hint: trimIndent() removes common leading spaces from all lines [OK]

Common Mistakes:

• Expecting original indentation to remain
• Confusing trimIndent() with trim() which removes only ends
• Thinking output is a single line string

4. Identify the error in this Kotlin code snippet using multiline strings and trimIndent():

val message = """
  Hello
    World
"".trimIndent()
println(message)

medium

A. Missing one double quote in the closing triple quotes.

B. The closing triple quotes should be """ not "".

C. No error; code runs and prints correctly.

D. Incorrect use of trimIndent() on a non-multiline string.

Solution

1. Step 1: Check triple quote syntax

   Multiline strings require triple double quotes """ at start and end.

2. Step 2: Identify the closing quotes

   The code uses only two double quotes "" at the end, which is invalid syntax.

3. Step 3: Correct the closing quotes

   It should be """ to properly close the multiline string.

4. Final Answer:

   The closing triple quotes should be """ not "". -> Option B

5. Quick Check:

   Triple quotes must match at start and end [OK]

Hint: Always close multiline strings with triple quotes """ [OK]

Common Mistakes:

• Using two quotes instead of three to close multiline strings
• Assuming trimIndent() fixes quote errors
• Confusing trimIndent() with trimming quotes

5. You want to create a multiline string in Kotlin that shows a list of fruits without extra indentation in the output. Which code snippet correctly achieves this using trimIndent()?

hard

A. val fruits = """
- Apple
- Banana
- Cherry
""".trimIndent()
println(fruits)

B. val fruits = """
- Apple
- Banana
- Cherry
""".trimIndent()
println(fruits)

C. val fruits = """
- Apple
- Banana
- Cherry
""".trimIndent()
println(fruits)

D. val fruits = "- Apple\n- Banana\n- Cherry".trimIndent()
println(fruits)

Solution

1. Step 1: Understand trimIndent() effect on indentation

   trimIndent() removes the common leading spaces from all lines, aligning text properly.

2. Step 2: Check each option's indentation

   val fruits = """ - Apple - Banana - Cherry """.trimIndent() println(fruits) has consistent 4-space indentation on each line, so trimIndent() will remove it neatly.

3. Step 3: Evaluate other options

   val fruits = """ - Apple - Banana - Cherry """.trimIndent() println(fruits) has uneven indentation, so trimIndent() removes nothing and leaves extra spaces on some lines. val fruits = """ - Apple - Banana - Cherry """.trimIndent() println(fruits) has uneven indentation, so trimIndent() won't align all lines properly. val fruits = "- Apple\n- Banana\n- Cherry".trimIndent() println(fruits) is a normal string, trimIndent() has no effect.

4. Final Answer:

   val fruits = """ - Apple - Banana - Cherry """.trimIndent() println(fruits) -> Option A

5. Quick Check:

   Consistent indentation + trimIndent() = neat output [OK]

Hint: Use consistent indentation inside triple quotes before trimIndent() [OK]

Common Mistakes:

• Using uneven indentation causing partial trimming
• Not using triple quotes for multiline strings
• Expecting trimIndent() to fix uneven spaces