Switch vs if comparison in Java - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print the day name using switch.

Java

int day = 3;
switch(day) {
    case 1:
        System.out.println("Monday");
        break;
    case 2:
        System.out.println("Tuesday");
        break;
    case [1]:
        System.out.println("Wednesday");
        break;
    default:
        System.out.println("Other day");
}

Drag options to blanks, or click blank then click option'

A3

B4

C5

D6

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong case number that does not match the day variable.

Forgetting the break statement after the case.

The case for day 3 should print "Wednesday". So, the blank must be filled with 3.

2fill in blank

medium

Complete the if statement to check if the variable 'score' is greater than or equal to 90.

Java

int score = 95;
if (score [1] 90) {
    System.out.println("Excellent");
} else {
    System.out.println("Keep trying");
}

Drag options to blanks, or click blank then click option'

A>=

B<

C==

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>='.

Using '==' which checks for equality only.

To check if score is greater than or equal to 90, use '>=' operator.

3fill in blank

hard

Fix the error in the switch statement to correctly handle the variable 'option'.

Java

char option = 'B';
switch([1]) {
    case 'A':
        System.out.println("Option A selected");
        break;
    case 'B':
        System.out.println("Option B selected");
        break;
    default:
        System.out.println("Invalid option");
}

Drag options to blanks, or click blank then click option'

AOption

Boption

C'option'

Doptions

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name with wrong capitalization.

Putting the variable name in quotes, making it a char literal.

The switch must use the variable 'option' exactly as declared, case sensitive and without quotes.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps words to their lengths only if length is greater than 3.

Java

Map<String, Integer> wordLengths = words.stream()
    .filter(word -> word.length() [1] 3)
    .collect(Collectors.toMap(word -> word, word -> word.[2]()));

Drag options to blanks, or click blank then click option'

A>

Blength()

CtoUpperCase()

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' in filter.

Using toUpperCase() instead of length() for value mapping.

The filter should keep words with length greater than 3, so use '>'. The value mapper uses word.length() to get length.

5fill in blank

hard

Fill all three blanks to create a switch statement that prints the season name based on the month number.

Java

int month = 4;
switch (month) {
    case [1]:
    case [2]:
    case [3]:
        System.out.println("Spring");
        break;
    default:
        System.out.println("Other season");
}

Drag options to blanks, or click blank then click option'

A3

B4

C5

D6

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong month numbers for Spring.

Not grouping multiple cases before break.

Months 3, 4, and 5 correspond to Spring season, so these cases print "Spring".

Practice

1. Which statement best describes when to use switch instead of if in Java?

easy

A. switch is best for checking many fixed values of a single variable.

B. switch can handle complex conditions like ranges easily.

C. if is only for checking equality, not ranges.

D. if cannot be used with multiple conditions.

Solution

1. Step 1: Understand switch usage

   switch works well when you have one variable and many fixed values to compare against.

2. Step 2: Compare with if

   if can handle any condition, including ranges and complex expressions, but switch is simpler for fixed values.

3. Final Answer:

   switch is best for checking many fixed values of a single variable. -> Option A

4. Quick Check:

   Use switch for fixed values = B [OK]

Hint: Use switch for fixed values, if for ranges or complex checks [OK]

Common Mistakes:

• Thinking switch can handle ranges
• Believing if is only for equality
• Assuming switch works with multiple variables
• Confusing switch with if-else chains

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

easy

A. switch (variable) { case 1: doSomething(); break; default: doDefault(); }

B. switch variable { case 1: doSomething(); break; default: doDefault(); }

C. switch (variable) do { case 1: doSomething(); break; default: doDefault(); }

D. switch (variable) { case 1 doSomething(); break; default doDefault(); }

Solution

1. Step 1: Check switch syntax structure

   The correct syntax requires parentheses around the variable and braces enclosing cases.

2. Step 2: Verify case and break usage

   Each case ends with a colon and usually a break statement to prevent fall-through.

3. Final Answer:

   switch (variable) { case 1: doSomething(); break; default: doDefault(); } -> Option A

4. Quick Check:

   Correct switch syntax uses parentheses and colons = A [OK]

Hint: Remember switch needs parentheses and colons for cases [OK]

Common Mistakes:

• Omitting parentheses around variable
• Using braces instead of colons after case
• Missing break statements causing fall-through
• Incorrect placement of default case

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

int day = 3;
switch(day) {
  case 1: System.out.println("Monday"); break;
  case 2: System.out.println("Tuesday"); break;
  case 3: System.out.println("Wednesday"); break;
  default: System.out.println("Invalid day");
}

medium

A. Monday

B. Tuesday

C. Invalid day

D. Wednesday

Solution

1. Step 1: Identify the value of day

   The variable day is set to 3.

2. Step 2: Match day with switch cases

   The case for 3 prints "Wednesday" and then breaks, so no other cases run.

3. Final Answer:

   Wednesday -> Option D

4. Quick Check:

   day=3 matches case 3 = C [OK]

Hint: Match variable value to case label, then print [OK]

Common Mistakes:

• Forgetting break causes fall-through
• Choosing default instead of matching case
• Confusing case numbers
• Assuming if-else output instead of switch

4. Identify the error in this Java code snippet:

int score = 85;
switch(score) {
  case score >= 90: System.out.println("A grade"); break;
  case score >= 80: System.out.println("B grade"); break;
  default: System.out.println("Fail");
}

medium

A. Missing break statements after cases.

B. Cannot use relational expressions in case labels.

C. Switch variable must be a String, not int.

D. Default case must be last.

Solution

1. Step 1: Understand switch case label restrictions

   Case labels must be constant values, not expressions like 'score >= 90'.

2. Step 2: Identify why relational expressions cause error

   Relational expressions are evaluated at runtime and cannot be used as case labels in switch.

3. Final Answer:

   Cannot use relational expressions in case labels. -> Option B

4. Quick Check:

   Case labels must be constants = A [OK]

Hint: Case labels must be constants, not conditions [OK]

Common Mistakes:

• Trying to use ranges in switch cases
• Forgetting case labels must be constant
• Assuming switch supports boolean expressions
• Misplacing default case

5. You want to print a message based on an integer score: "Excellent" if score >= 90, "Good" if score >= 75, "Average" if score >= 50, and "Poor" otherwise. Which approach is best in Java?

hard

A. Use a switch statement with case labels for each range.

B. Use a switch with string values for score.

C. Use nested if-else statements to check ranges.

D. Use a switch with boolean expressions in cases.

Solution

1. Step 1: Analyze the conditions

   The conditions involve ranges (score >= 90, >= 75, etc.) which cannot be directly used in switch cases.

2. Step 2: Choose the suitable control structure

   if-else statements can handle ranges and complex conditions easily, unlike switch.

3. Final Answer:

   Use nested if-else statements to check ranges. -> Option C

4. Quick Check:

   Ranges need if-else, not switch = D [OK]

Hint: Use if-else for ranges, switch only for fixed values [OK]

Common Mistakes:

• Trying to use switch for range conditions
• Using boolean expressions in switch cases
• Assuming switch works with strings for numbers
• Ignoring else for default case