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

Using Labeled break and continue in Java

📖 Scenario: Imagine you are managing a small warehouse with shelves and boxes. You want to find a specific box labeled "Target" among shelves and boxes. Sometimes you want to skip checking certain boxes or stop searching entirely when you find the target.

🎯 Goal: You will write a Java program that uses labeled break and labeled continue to control loops while searching for the "Target" box in a 2D array representing shelves and boxes.

📋 What You'll Learn

Create a 2D array called shelves with specific box labels.

Create a label called search for the outer loop.

Use labeled continue to skip boxes labeled "Skip".

Use labeled break to stop searching when the "Target" box is found.

Print the position of the "Target" box when found.

💡 Why This Matters

🌍 Real World

Labeled break and continue help manage complex nested loops, such as searching in grids, processing tables, or handling multi-level menus.

💼 Career

Understanding labeled break and continue is useful for writing clear and efficient code in Java, especially in jobs involving data processing, game development, or UI programming.

1

Create the shelves data structure

Create a 2D String array called shelves with these exact values: {{"Box1", "Box2", "Skip"}, {"Box3", "Target", "Box4"}, {"Skip", "Box5", "Box6"}}.

Java

# Create the 2D array shelves with the given box labels
# Your code here

Hint

Use String[][] shelves = { ... }; with the exact rows and columns.

2

Add the labeled outer loop

Add a labeled outer for loop with label search to iterate over the rows of shelves using variable i.

Java

String[][] shelves = {
    {"Box1", "Box2", "Skip"},
    {"Box3", "Target", "Box4"},
    {"Skip", "Box5", "Box6"}
};

// Add labeled outer loop here
# Your code here

Hint

Write search: before the outer for loop.

3

Add inner loop with labeled continue and break

Inside the search loop, add an inner for loop with variable j to iterate over shelves[i]. Use if to continue search when the box label is "Skip". Use if to break search when the box label is "Target". Print the found position with System.out.println("Found Target at shelf " + i + ", box " + j); before breaking.

Java

String[][] shelves = {
    {"Box1", "Box2", "Skip"},
    {"Box3", "Target", "Box4"},
    {"Skip", "Box5", "Box6"}
};

search:
for (int i = 0; i < shelves.length; i++) {
    // Add inner loop and labeled continue/break here
# Your code here

Hint

Use nested loops and labeled continue and break with the label search.

4

Print the final output

Run the program to print the position of the "Target" box found. The output should be exactly: Found Target at shelf 1, box 1.

Java

String[][] shelves = {
    {"Box1", "Box2", "Skip"},
    {"Box3", "Target", "Box4"},
    {"Skip", "Box5", "Box6"}
};

search:
for (int i = 0; i < shelves.length; i++) {
    for (int j = 0; j < shelves[i].length; j++) {
        if (shelves[i][j].equals("Skip")) {
            continue search;
        }
        if (shelves[i][j].equals("Target")) {
            // Print the found position here
# Your code here

Hint

Make sure the print statement matches exactly and the program runs fully.

Practice

1. What does a labeled break statement do in Java nested loops?

easy

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

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

C. It restarts the innermost loop from the beginning.

D. It exits the loop identified by the label immediately.

Solution

1. Step 1: Understand labeled break usage

   A labeled break exits the loop that has the specified label, not just the innermost loop.

2. Step 2: Compare with normal break

   Normal break exits only the innermost loop, but labeled break can exit outer loops directly.

3. Final Answer:

   It exits the loop identified by the label immediately. -> Option D

4. Quick Check:

   Labeled break = exit labeled loop [OK]

Hint: Labeled break jumps out of the named loop instantly [OK]

Common Mistakes:

• Confusing labeled break with continue
• Thinking it only affects the innermost loop
• Assuming it pauses instead of exits

2. Which of the following is the correct syntax for a labeled continue statement in Java?

easy

A. continue: labelName;

B. continue labelName;

C. continue (labelName);

D. continue->labelName;

Solution

1. Step 1: Recall labeled continue syntax

   The correct syntax is the keyword continue followed by the label name and a semicolon.

2. Step 2: Eliminate incorrect forms

   Java does not use colons, parentheses, or arrows with continue statements.

3. Final Answer:

   continue labelName; -> Option B

4. Quick Check:

   Correct labeled continue syntax = continue labelName; [OK]

Hint: Use 'continue' followed by label and semicolon [OK]

Common Mistakes:

• Adding colon after continue
• Using parentheses around label
• Using arrow symbols instead of space

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

outer:
for (int i = 1; i <= 3; i++) {
    inner:
    for (int j = 1; j <= 3; j++) {
        if (j == 2) continue outer;
        System.out.print(i + "-" + j + " ");
    }
}

medium

A. 1-1 2-1 3-1 3-2

B. 1-1 1-2 1-3 2-1 2-2 2-3 3-1 3-2 3-3

C. 1-1 2-1 3-1

D. 1-1 2-1 2-2 3-1 3-2

Solution

1. Step 1: Analyze loops and continue

   When j == 2, the statement continue outer; skips the rest of the current outer loop iteration and moves to the next i.

2. Step 2: Trace output

   For i=1, j=1 prints "1-1 ". At j=2, continue outer skips to i=2. Similarly for i=2 and i=3, only j=1 prints.

3. Final Answer:

   1-1 2-1 3-1 -> Option C

4. Quick Check:

   Labeled continue skips to next outer loop iteration [OK]

Hint: Labeled continue skips to next iteration of labeled loop [OK]

Common Mistakes:

• Thinking continue skips only inner loop
• Expecting all inner loop values to print
• Ignoring label effect on continue

4. Identify the error in this Java code snippet using labeled break:

outer:
for (int i = 0; i < 3; i++) {
    for (int j = 0; j < 3; j++) {
        if (i == j) break;
    }
}

medium

A. The label 'outer' is not used with break or continue.

B. The break statement should be 'break outer;' to use the label.

C. Labels cannot be used with for loops.

D. The code will cause a syntax error due to missing semicolon.

Solution

1. Step 1: Check label usage

   The label 'outer' is declared but never referenced by break or continue statements.

2. Step 2: Understand label necessity

   Labels must be used with break or continue to have effect; otherwise, they are redundant but not syntax errors.

3. Final Answer:

   The label 'outer' is not used with break or continue. -> Option A

4. Quick Check:

   Unused label = no effect but no syntax error [OK]

Hint: Use label only if break or continue references it [OK]

Common Mistakes:

• Assuming unused label causes syntax error
• Thinking break without label breaks outer loop
• Confusing label usage rules

5. Given nested loops, how would you use labeled break and continue to print only pairs (i, j) where i < j, skipping all others efficiently? Choose the correct code snippet.

hard

A. outer:
for (int i = 1; i <= 3; i++) {
inner:
for (int j = 1; j <= 3; j++) {
if (i >= j) continue inner;
System.out.print("(" + i + "," + j + ") ");
}
}

B. outer:
for (int i = 1; i <= 3; i++) {
inner:
for (int j = 1; j <= 3; j++) {
if (i >= j) break outer;
System.out.print("(" + i + "," + j + ") ");
}
}

C. outer:
for (int i = 1; i <= 3; i++) {
inner:
for (int j = 1; j <= 3; j++) {
if (i >= j) continue outer;
System.out.print("(" + i + "," + j + ") ");
}
}

D. outer:
for (int i = 1; i <= 3; i++) {
inner:
for (int j = 1; j <= 3; j++) {
if (i >= j) break inner;
System.out.print("(" + i + "," + j + ") ");
}
}

Solution

1. Step 1: Understand the condition and loops

   We want to print pairs where i < j only. If i >= j, skip to next j (inner loop iteration).

2. Step 2: Analyze each option's control flow

   outer: for (int i = 1; i <= 3; i++) { inner: for (int j = 1; j <= 3; j++) { if (i >= j) continue inner; System.out.print("(" + i + "," + j + ") "); } } uses continue inner; to skip the current iteration and move to next j, efficiently skipping invalid pairs.

3. Final Answer:

   Uses continue inner; to skip when i >= j. -> Option A

4. Quick Check:

   Labeled continue to inner loop skips invalid pairs [OK]

Hint: Use 'continue inner;' to skip to next inner loop iteration [OK]

Common Mistakes:

• Using break outer which stops all loops
• Using continue outer which skips valid pairs as well
• Using break inner which stops inner loop prematurely