Labeled break and continue in Kotlin - Mini Project: Build & Apply

Using Labeled break and continue in Kotlin

📖 Scenario: Imagine you are organizing a small sports event. You have a list of teams and their players. You want to find the first team that has a player named "Alex" and stop searching once you find it. Also, you want to skip any team that has no players.

🎯 Goal: You will write a Kotlin program that uses labeled break and continue statements to efficiently search through teams and players.

📋 What You'll Learn

Create a map called teams with exactly these entries: "Tigers" with players ["John", "Alex", "Sam"], "Lions" with players [], and "Bears" with players ["Mike", "Anna"].

Create a Boolean variable called foundAlex and set it to false.

Use a labeled for loop named teamLoop to iterate over teams. Inside, skip teams with no players using a labeled continue. If a player named "Alex" is found, set foundAlex to true and use a labeled break to exit the outer loop.

Print "Found Alex in team: <teamName>" if foundAlex is true, otherwise print "Alex not found in any team".

💡 Why This Matters

🌍 Real World

Using labeled break and continue helps when searching through complex data like teams and players, allowing you to stop or skip parts efficiently.

💼 Career

Understanding labeled loops is useful in software development when working with nested data structures or complex loops, improving code clarity and performance.

1

Create the teams map

Create a map called teams with these exact entries: "Tigers" with players ["John", "Alex", "Sam"], "Lions" with players [], and "Bears" with players ["Mike", "Anna"].

Kotlin

# Create the teams map with the exact entries
# Your code here

Hint

Use mapOf to create the map. Each team name maps to a list of player names.

2

Create the foundAlex variable

Create a Boolean variable called foundAlex and set it to false.

Kotlin

val teams = mapOf(
    "Tigers" to listOf("John", "Alex", "Sam"),
    "Lions" to listOf(),
    "Bears" to listOf("Mike", "Anna")
)

# Create foundAlex variable and set it to false
# Your code here

Hint

Use var to create a variable that can change later.

3

Use labeled loops with break and continue

Use a labeled for loop named teamLoop to iterate over teams. Inside, skip teams with no players using a labeled continue. If a player named "Alex" is found, set foundAlex to true and use a labeled break to exit the outer loop.

Kotlin

val teams = mapOf(
    "Tigers" to listOf("John", "Alex", "Sam"),
    "Lions" to listOf(),
    "Bears" to listOf("Mike", "Anna")
)

var foundAlex = false

# Use labeled loops to find "Alex" and skip empty teams
# Your code here

Hint

Label the outer loop with teamLoop@. Use continue@teamLoop to skip empty teams. Use break@teamLoop to stop searching when "Alex" is found.

4

Print the result

Print "Found Alex in team: <teamName>" if foundAlex is true, otherwise print "Alex not found in any team". Use the variable teamName from the loop where foundAlex was set.

Kotlin

val teams = mapOf(
    "Tigers" to listOf("John", "Alex", "Sam"),
    "Lions" to listOf(),
    "Bears" to listOf("Mike", "Anna")
)

var foundAlex = false

teamLoop@ for ((teamName, players) in teams) {
    if (players.isEmpty()) continue@teamLoop
    for (player in players) {
        if (player == "Alex") {
            foundAlex = true
            break@teamLoop
        }
    }
}

# Print the result based on foundAlex
# Your code here

Hint

Remember to store the team name when you find Alex, so you can print it after the loops.

Practice

1. What does the break@label statement do in Kotlin nested loops?

easy

A. It stops the loop identified by the label immediately.

B. It skips the current iteration of the innermost loop.

C. It restarts the entire program from the beginning.

D. It pauses the loop until a condition is met.

Solution

1. Step 1: Understand labeled break usage

   The break@label statement is used to exit a specific loop marked by the label, not just the innermost loop.

2. Step 2: Compare with other options

   Options B and D describe continue or pause behavior, which is incorrect. It restarts the entire program from the beginning. is unrelated to loop control.

3. Final Answer:

   It stops the loop identified by the label immediately. -> Option A

4. Quick Check:

   break@label stops labeled loop [OK]

Hint: break@label exits the labeled loop immediately [OK]

Common Mistakes:

• Confusing break@label with continue@label
• Thinking break@label only stops innermost loop
• Assuming break@label pauses instead of stops

2. Which of the following is the correct syntax to continue the outer loop labeled outerLoop in Kotlin?

easy

A. continue#outerLoop

B. continue outerLoop

C. continue(outerLoop)

D. continue@outerLoop

Solution

1. Step 1: Recall Kotlin labeled continue syntax

   Kotlin uses the @ symbol to refer to labels with break or continue, so the correct syntax is continue@label.

2. Step 2: Eliminate incorrect options

   Options B, C, and D use invalid syntax for labels in Kotlin.

3. Final Answer:

   continue@outerLoop -> Option D

4. Quick Check:

   Use continue@label to continue labeled loop [OK]

Hint: Use @ symbol with label for continue or break [OK]

Common Mistakes:

• Omitting @ symbol before label
• Using parentheses or other symbols with label
• Confusing syntax with other languages

3. What is the output of the following Kotlin code?

outer@ for (i in 1..3) {
    inner@ for (j in 1..3) {
        if (i == 2 && j == 2) break@outer
        print("$i$j ")
    }
}

medium

A. 11 12 13 21 22

B. 11 12 13 21

C. 11 12 13 21 22 23

D. 11 12 13

Solution

1. Step 1: Trace nested loops and break condition

   The outer loop runs i=1 to 3, inner loop j=1 to 3. When i=2 and j=2, break@outer stops the outer loop entirely.

2. Step 2: List printed values before break

   For i=1, j=1..3 prints 11 12 13. For i=2, j=1 prints 21, then at j=2 break@outer stops all loops. So output is "11 12 13 21".

3. Final Answer:

   11 12 13 21 -> Option B

4. Quick Check:

   break@outer stops all loops at i=2,j=2 [OK]

Hint: break@label stops all loops at labeled point [OK]

Common Mistakes:

• Assuming break@outer only stops inner loop
• Including values after break condition
• Confusing break@outer with continue@outer

4. Identify the error in this Kotlin code snippet:

outer@ for (i in 1..2) {
    for (j in 1..2) {
        if (i == 1) continue outer
        println("i=$i, j=$j")
    }
}

medium

A. continue@outer should be used instead of continue outer.

B. continue cannot be used with a label on an inner loop.

C. Label 'outer' is not defined.

D. No error; code runs correctly.

Solution

1. Step 1: Check labeled continue syntax

   Kotlin requires the @ symbol when using labels with break or continue, so it must be continue@outer.

2. Step 2: Verify label definition and usage

   The label 'outer' is correctly defined, so Label 'outer' is not defined. is wrong. Using continue with label without @ causes syntax error.

3. Final Answer:

   continue@outer should be used instead of continue outer. -> Option A

4. Quick Check:

   Use continue@label syntax to avoid errors [OK]

Hint: Always use @ with label in continue or break [OK]

Common Mistakes:

• Omitting @ symbol in labeled continue
• Thinking label must be on inner loop
• Assuming no error when syntax is wrong

5. Given nested loops labeled outer and inner, how can you skip only the current iteration of the outer loop when a condition in the inner loop is met?

hard

A. Use break@outer inside inner loop.

B. Use continue without label inside inner loop.

C. Use continue@outer inside inner loop.

D. Use break without label inside inner loop.

Solution

1. Step 1: Understand labeled continue effect

   Using continue@outer skips the current iteration of the outer loop, moving to the next iteration of outer.

2. Step 2: Compare with break and unlabeled continue

   break@outer would exit the outer loop entirely, not just skip iteration. Unlabeled continue affects only inner loop.

3. Final Answer:

   Use continue@outer inside inner loop. -> Option C

4. Quick Check:

   continue@outer skips outer loop iteration [OK]

Hint: Use continue@label to skip labeled loop iteration [OK]

Common Mistakes:

• Using break@outer instead of continue@outer
• Using unlabeled continue to skip outer loop
• Confusing break and continue effects