Checked exceptions (subclasses of Exception, excluding RuntimeException) must be either caught or declared with `throws` — the compiler enforces this. Unchecked exceptions (subclasses of RuntimeException) don't require explicit handling and typically represent programming bugs rather than recoverable conditions.

Intermediate5 min

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#Checked Exceptions#Unchecked Exceptions

Checked Exceptions

Examples: IOException, SQLException. These represent conditions a well-written program should anticipate and recover from (like a missing file), so the compiler forces you to acknowledge them via try-catch or a throws declaration.

Unchecked Exceptions

Examples: NullPointerException, ArrayIndexOutOfBoundsException, IllegalArgumentException. These typically indicate a bug in the code rather than an expected failure condition, so the compiler doesn't force handling — though you still can catch them.

Throwable → Error (unrecoverable) & Exception → RuntimeException (unchecked) & other Exception subclasses (checked)

Checked vs Unchecked

java

// Checked: must declare or catch
void readFile(String path) throws IOException {
    Files.readAllLines(Paths.get(path));
}

// Unchecked: compiler doesn't force handling
void divide(int a, int b) {
    System.out.println(a / b);   // may throw ArithmeticException
}

Interview Answer

Checked exceptions are part of a method's contract — the compiler forces callers to handle them, typically for recoverable, expected failure conditions like I/O. Unchecked exceptions (RuntimeException and its subclasses) usually signal programmer errors, and Java doesn't force you to handle them everywhere since that would clutter code with defensive catches for things that shouldn't happen if the code is correct.