Checked vs Unchecked Exceptions in Java — A Deep Dive
Every Java developer hits exceptions early. But the difference between checked and unchecked exceptions — and when to use which — trips people up for years. This post goes deep.
The Exception Hierarchy
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Everything starts from Throwable:
Throwable ├── Error (unchecked — don't catch these) │ ├── OutOfMemoryError │ ├── StackOverflowError │ └── ... └── Exception (checked — must handle or declare) ├── IOException ├── SQLException ├── ... └── RuntimeException (unchecked — optional to handle) ├── NullPointerException ├── IllegalArgumentException ├── ArrayIndexOutOfBoundsException └── ...
The rule is simple: