Switch statement in Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of switch with pattern matching

What is the output of the following Java code using switch with pattern matching?

Java

Object obj = 123;
String result = switch (obj) {
    case Integer i -> "Integer: " + i;
    case String s -> "String: " + s;
    default -> "Unknown";
};
System.out.println(result);

A String: 123

B Integer: 123

C Unknown

D Compilation error

💡 Hint

Remember that the switch matches the first compatible case.

The object is an Integer with value 123, so the case Integer i matches and returns "Integer: 123".

❓ Predict Output

intermediate

Switch expression with yield

What will be printed by this Java code using switch expression with yield?

Java

int day = 3;
String dayName = switch (day) {
    case 1 -> "Monday";
    case 2 -> "Tuesday";
    case 3 -> {
        yield "Wednesday";
    }
    default -> "Invalid";
};
System.out.println(dayName);

A Wednesday

B Invalid

C Compilation error

D null

💡 Hint

The yield keyword returns a value from a block in a switch expression.

For day = 3, the switch block uses yield to return "Wednesday".

❓ Predict Output

advanced

Switch with multiple labels and fall-through

What is the output of this Java switch statement?

Java

int num = 2;
switch (num) {
    case 1, 2, 3:
        System.out.print("Low");
    case 4:
        System.out.print(" Medium");
        break;
    default:
        System.out.print(" High");
}

A Low

B Medium

C Low Medium

D Low Medium High

💡 Hint

Without break after case 1,2,3, execution falls through to case 4.

Case 2 matches, prints "Low", then falls through to case 4, prints " Medium", then breaks.

❓ Predict Output

advanced

Switch expression with sealed classes

Given sealed classes and a switch expression, what is the output?

Java

sealed interface Shape permits Circle, Square {}
record Circle(double radius) implements Shape {}
record Square(double side) implements Shape {}

Shape shape = new Circle(2.0);
String desc = switch (shape) {
    case Circle c -> "Circle with radius " + c.radius();
    case Square s -> "Square with side " + s.side();
};
System.out.println(desc);

A Compilation error due to missing default

B Square with side 2.0

C Runtime exception

D Circle with radius 2.0

💡 Hint

Sealed interfaces allow exhaustive switch without default.

The shape is a Circle with radius 2.0, so the first case matches and returns the description.

❓ Predict Output

expert

Switch expression with null and pattern matching

What happens when this Java code runs?

Java

Object obj = null;
String result = switch (obj) {
    case String s -> "String: " + s;
    case null -> "Null value";
    default -> "Other";
};
System.out.println(result);

A Compilation error: 'case null' not allowed

B Other

C Null value

D Runtime NullPointerException

💡 Hint

Java switch does not allow 'case null' labels.

Java switch expressions do not support 'case null' labels, so this code does not compile.