Checked & Unchecked Exception in Java
Introduction
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Definition:
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Checked Exception:
- Exceptions that are checked at compile-time by the compiler are known as Checked Exception.
- If checked exceptions are not handled (using try-catch or throws), the code will not compile.
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Unchecked Exception:
- Exceptions that are ignored by compiler and not checked at compile-time but occur at runtime are known as Unchecked Exception.
- Compiler does not force to handle the unchecked exceptions, but the program may crash if not handled.
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Checked Exception:
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Real-World Analogy:
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Checked Exception:
- For Example : A scheduled train delay notice → we are informed in advance, and we must plan accordingly.
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Unchecked Exception:
- For Example : A sudden tire burst while driving → happens unexpectedly, no prior warning.
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Checked Exception:
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Hierarchy:
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Checked Exception:
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Checked Exceptions are subclasses of
Exceptionclass excludingRuntimeException.
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Checked Exceptions are subclasses of
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Unchecked Exception:
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Unchecked Exceptions are subclasses of
RuntimeExceptionand allErrorclasses.
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Unchecked Exceptions are subclasses of
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Checked Exception:
Below are some differences between Error and Exception:
| Aspect | Checked Exception | Unchecked Exception |
|---|---|---|
| Also Called | Compile-Time Exceptions | Runtime Exceptions |
| Definition | Checked Exceptions are those which are checked at compile-time by compiler | Unchecked Exceptions are those which are ignored by compiler and checked at runtime by JVM |
| Hierarchy | Comes under the Exception class,(excluding RuntimeException) |
Comes under the RuntimeException class |
| Examples | IOException, SQLException |
NullPointerException, ArithmeticException |
| Handling | Must handled by try-catch or declared using throws keyword |
Optional to handle (but recommended) |
| When occur | External factors (eg. I/O and DB connection) | Code mistakes (eg. null, index, /0) |
| Impact | Safe but lengthy | Flexible but risky |
| Analogy | Train delay notice | Tire burst |
| Best Practice | Always handle or declare checked exceptions properly | Avoid mistakes in code or Check data before use |
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