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Java Exception Handling Practice

try-catch, checked vs unchecked exceptions, custom exceptions and throws.

Arithmetic Exception

Easy

Read two integers A and B. If B is 0, print "Cannot divide by zero"; otherwise print A / B. Use a try-catch around the division.

Input Format

A single line with two integers A B.

Output Format

The quotient, or "Cannot divide by zero".

Sample Test Cases

Sample Input 1 10 2	Sample Output 1 5
Sample Input 2 10 0	Sample Output 2 Cannot divide by zero

Constraints

-10^6

Explanation

Catch ArithmeticException.

Array Index Exception

Easy

Read N, then N integers, then an index K. Print the element at K; if K is out of range print "Index out of range". Use try-catch.

Input Format

First line: N. Second line: N ints. Third line: K.

Output Format

Element or "Index out of range".

Sample Test Cases

Sample Input 1 3 10 20 30 1	Sample Output 1 20
Sample Input 2 3 10 20 30 9	Sample Output 2 Index out of range

Constraints

Explanation

Catch ArrayIndexOutOfBoundsException.

Number Format Exception

Easy

Read a string S. Try to parse it as an integer with Integer.parseInt. On success print the number times 2; on failure print "Invalid number".

Input Format

A single line containing a string.

Output Format

The doubled integer or "Invalid number".

Sample Test Cases

Sample Input 1 21	Sample Output 1 42
Sample Input 2 abc	Sample Output 2 Invalid number

Constraints

S length

Explanation

Catch NumberFormatException.

Try-Catch-Finally

Medium

Read an integer N. Print "Inside try" before any operation. If N is negative, the code throws IllegalArgumentException. Always print "Inside finally".

Input Format

A single integer N.

Output Format

Inside try, then an error message or no extra line, then Inside finally.

Sample Test Cases

Sample Input 1 5	Sample Output 1 Inside try Inside finally
Sample Input 2 -1	Sample Output 2 Inside try Caught exception Inside finally

Constraints

Any integer.

Explanation

finally always runs.

Multiple Catch Blocks

Medium

Read a string and an index K. Try Integer.parseInt(string) (may throw NumberFormatException) then charAt(K) on the result string...

Input Format

First line: a string. Second line: an integer K.

Output Format

On success the char at K, else the first caught message: "Number format error" or "Index out of range".

Sample Test Cases

Sample Input 1 hello 1	Sample Output 1 e
Sample Input 2 123 5	Sample Output 2 Index out of range

Constraints

String length

Explanation

Order catch blocks from specific to general.

Nested Try

Medium

Read two integers A and B. Use an outer try with an inner try that divides A by B. If B is 0, the inner catch prints "Inner: division error"; the outer catch prints "Outer: caught".

Input Format

A single line with two integers A B.

Output Format

The quotient, or "Inner: division error".

Sample Test Cases

Sample Input 1 10 2	Sample Output 1 5
Sample Input 2 10 0	Sample Output 2 Inner: division error

Constraints

B may be 0.

Explanation

Inner catches its own exception first.

Throwing an Exception

Medium

Read an age. If it is below 18, throw an IllegalArgumentException with message "Not eligible"; catch it in main and print the message. Otherwise print "Eligible".

Input Format

A single integer age.

Output Format

Eligible, or the exception message.

Sample Test Cases

Sample Input 1 20	Sample Output 1 Eligible
Sample Input 2 16	Sample Output 2 Not eligible

Constraints

Explanation

throw new IllegalArgumentException(...).

Checked Exception (File)

Hard

Read a file name. Try to create a new File(name) and call createNewFile() inside a try-catch for IOException. Print "File created" on success (ignore the boolean) or "IO error" on failure.

Input Format

A single line: a file name.

Output Format

"File created" or "IO error".

Sample Test Cases

Sample Input 1 demo.txt	Sample Output 1 File created
Sample Input 2	Sample Output 2 IO error

Constraints

Any file name.

Explanation

createNewFile() throws IOException (checked).

Custom Exception

Hard

Create a custom exception class InvalidAgeException extends Exception. In main, read age; if < 18 throw it (declared via throws on main or caught) and print "Custom: "; else print "Valid".

Input Format

A single integer age.

Output Format

Valid, or Custom: Age must be 18+.

Sample Test Cases

Sample Input 1 22	Sample Output 1 Valid
Sample Input 2 15	Sample Output 2 Custom: Age must be 18+

Constraints

Explanation

Your custom class extends Exception.

Exception Propagation

Hard

Write a method static void check(int n) that throws IllegalArgumentException when n is negative. main calls check(N) inside try-catch. If N is negative the message is "Negative not allowed"; otherwise print "Ok".

Input Format

A single integer N.

Output Format

Ok, or Negative not allowed.

Sample Test Cases

Sample Input 1 10	Sample Output 1 Ok
Sample Input 2 -3	Sample Output 2 Negative not allowed

Constraints

Any integer.

Explanation

Propagate with throw, handle in main.

Finally with Return

Hard

Write a method static String test(int n) that returns "Positive" for n > 0 else "Non-positive", but always prints "Finally block" before returning (use finally). Print the method result.

Input Format

A single integer N.

Output Format

Two lines: Finally block, then the result.

Sample Test Cases

Sample Input 1 5	Sample Output 1 Finally block Positive
Sample Input 2 0	Sample Output 2 Finally block Non-positive

Constraints

Any integer.

Explanation

finally executes even before return.

Unchecked vs Checked

Hard

Read an integer N. If N == 1, cause an ArrayIndexOutOfBoundsException and catch it, printing "Unchecked caught". Otherwise print "No exception".

Input Format

A single integer N.

Output Format

"Unchecked caught" or "No exception".

Sample Test Cases

Sample Input 1 1	Sample Output 1 Unchecked caught
Sample Input 2 2	Sample Output 2 No exception

Constraints

Explanation

Runtime exceptions need no throws clause.

Competitive MCQs — Java Exception Handling

Code snippets, output prediction, concepts & error spotting. Pick an answer to see instant feedback.

Score 0/ 33

Which keyword starts a block that may throw an exception?

Correct!

Wrong — correct answer is .

Code that may fail is wrapped in a try block.

Which keyword catches an exception?

Correct!

Wrong — correct answer is .

Java uses try-catch; except is Python.

What is the output of this code?

java

try {
    int x = 10 / 0;
} catch (ArithmeticException e) {
    System.out.println("Error");
}

Correct!

Wrong — correct answer is .

10 / 0 throws ArithmeticException, caught → "Error".

What is the output of this code?
try {
int x = 10 / 0;
} catch (ArithmeticException e) {
System.out.println("Error");
}

Correct!

Wrong — correct answer is .

10 / 0 throws ArithmeticException, caught → "Error".

Which block always executes after try/catch?

Correct!

Wrong — correct answer is .

finally runs regardless of whether an exception occurred.

Which is the base class of all checked exceptions?

Correct!

Wrong — correct answer is .

Exception is the base of checked exceptions.

What is the output of this code?

java

int[] a = {1, 2};
try {
    System.out.println(a[5]);
} catch (ArrayIndexOutOfBoundsException e) {
    System.out.println("Bad index");
}

Correct!

Wrong — correct answer is .

a[5] throws ArrayIndexOutOfBoundsException → "Bad index".

What is the output of this code?
int[] a = {1, 2};
try {
System.out.println(a[5]);
} catch (ArrayIndexOutOfBoundsException e) {
System.out.println("Bad index");
}

Correct!

Wrong — correct answer is .

a[5] throws ArrayIndexOutOfBoundsException → "Bad index".

Which keyword deliberately throws an exception?

Correct!

Wrong — correct answer is .

throw creates/exits with an exception; throws declares them.

Q10

What is the difference between checked and unchecked exceptions?

Correct!

Wrong — correct answer is .

Checked exceptions are enforced by the compiler.

Q11

Which is an unchecked (runtime) exception?

Correct!

Wrong — correct answer is .

NullPointerException extends RuntimeException (unchecked).

Q12

What is the output of this code?

java

try {
    System.out.print("A");
} finally {
    System.out.print("B");
}

Correct!

Wrong — correct answer is .

Both run — finally needs no exception to execute.

Q13

What is the output of this code?
try {
System.out.print("A");
} finally {
System.out.print("B");
}

Correct!

Wrong — correct answer is .

Both run — finally needs no exception to execute.

Q14

What is the output of this code?
try {
int[] a = new int[2];
System.out.println(a[5]);
} catch (ArrayIndexOutOfBoundsException e) {
System.out.println("caught");
}

Correct!

Wrong — correct answer is .

a[5] is out of bounds and caught by the handler.

Q15

What does the finally block guarantee?

Correct!

Wrong — correct answer is .

finally executes in all paths for cleanup.

Q16

Which exception is thrown for dividing an int by zero?

Correct!

Wrong — correct answer is .

Integer division by zero throws ArithmeticException.

Q17

What is the output of this code?
try {
int x = 10 / 0;
} catch (ArithmeticException e) {
System.out.println("math");
} catch (Exception e) {
System.out.println("any");
}

Correct!

Wrong — correct answer is .

ArithmeticException matches the first catch.

Q18

What is an unchecked exception?

Correct!

Wrong — correct answer is .

Unchecked exceptions extend RuntimeException.

Q19

Which of these is checked?

Correct!

Wrong — correct answer is .

IOException is checked; the others are runtime exceptions.

Q20

What is the output of this code?
try {
throw new IllegalStateException("bad");
} catch (IllegalStateException e) {
System.out.println(e.getMessage());
}

Correct!

Wrong — correct answer is .

getMessage() returns the message "bad".

Q21

Which keyword declares that a method may throw a checked exception?

Correct!

Wrong — correct answer is .

throws appears in the method signature to declare checked exceptions.

Q22

Which keyword actually raises an exception?

Correct!

Wrong — correct answer is .

throw new Exception() creates and raises an exception.

Q23

What is the output of this code?
try {
System.out.print("1");
return;
} finally {
System.out.print("2");
}

Correct!

Wrong — correct answer is .

finally runs before the return completes, printing 2.

Q24

What is the base class for checked exceptions?

Correct!

Wrong — correct answer is .

Checked exceptions derive from Exception (excluding RuntimeException).

Q25

What is the output of this code?
String s = null;
try {
System.out.println(s.length());
} catch (NullPointerException e) {
System.out.println("null");
}

Correct!

Wrong — correct answer is .

Calling length() on null throws NullPointerException.

Q26

What does printStackTrace() do?

Correct!

Wrong — correct answer is .

It logs the stack trace for debugging.

Q27

What is the output of this code?
try {
int x = Integer.parseInt("12a");
} catch (NumberFormatException e) {
System.out.println("nf");
}

Correct!

Wrong — correct answer is .

Parsing "12a" fails and throws NumberFormatException.

Q28

Which block is optional in try-catch?

Correct!

Wrong — correct answer is .

A try must have at least one catch or finally; each is otherwise optional.

Q29

What is a multi-catch?

Correct!

Wrong — correct answer is .

catch (A | B e) handles several types with one handler.

Q30

What is the output of this code?
try {
throw new RuntimeException("r");
} catch (RuntimeException e) {
System.out.println("runtime");
}

Correct!

Wrong — correct answer is .

The RuntimeException is caught and prints "runtime".

Q31

Which is the parent of all exceptions and errors?

Correct!

Wrong — correct answer is .

Throwable is the root for both Exception and Error.

Q32

What is the output of this code?
try {
System.out.println("try");
} catch (Exception e) {
System.out.println("catch");
}

Correct!

Wrong — correct answer is .

No exception is thrown, so only "try" prints.

Q33

What is an Error in Java exception hierarchy?

Correct!

Wrong — correct answer is .

Errors signal serious system problems usually not meant to be caught.

Java Practice Questions

Java Exception Handling Practice

Competitive MCQs — Java Exception Handling