docs/bugpattern/UnusedException.md

Catching an exception and throwing another is a common pattern. This is often
used to supply additional information, or to turn a checked exception into an
unchecked one.

```java
  try {
    ioLogic();
  } catch (IOException e) {
    throw new IllegalStateException(); // BAD
  }
```

Throwing a new exception without supplying the caught one as a cause means the
stack trace will terminate at the `catch` block, which will make debugging a
possible fault in `ioLogic()` far harder than is necessary.

Prefer wrapping the original exception instead,

```java
  try {
    ioLogic();
  } catch (IOException e) {
    throw new IllegalStateException(e); // GOOD
  }
```

## Suppression

If the exception is deliberately unused, rename it `_` or `unused` to suppress
this diagnostic.

```java
static <T extends Enum<T>> T tryForName(Class<T> enumType, String name) {
  try {
    return Enum.valueOf(enumType, name);
  } catch (IllegalArgumentException unused) {
    return null;
  }
}
```

Otherwise, suppress false positives with `@SuppressWarnings("UnusedException")`
on the ignored exception. Consider also adding a comment to explain why the
exception should not be propagated.

```java
  try {
    ...
  } catch (@SuppressWarnings("UnusedException") IOException e) {
    throw new IllegalStateException();
  }
```