public final Class Throwables

Gets a Throwable cause chain as a list. The first entry in the list will be throwable followed by its cause hierarchy. Note that this is a snapshot of the cause chain and will not reflect any subsequent changes to the cause chain.

Here's an example of how it can be used to find specific types of exceptions in the cause chain:

Iterables.filter(Throwables.getCausalChain(e), IOException.class));

Parameters

throwable:Throwable

the non-null Throwable to extract causes from

Returns:List<Throwable>

an unmodifiable list containing the cause chain starting with throwable

Exceptions

IllegalArgumentException:

if there is a loop in the causal chain

Returns throwable's cause, cast to expectedCauseType.

Prefer this method instead of manually casting an exception's cause. For example, (IOException) e.getCause() throws a ClassCastException that discards the original exception e if the cause is not an IOException, but Throwables.getCauseAs(e, IOException.class) keeps e as the ClassCastException's cause.

Annotations

@J2ktIncompatible

@GwtIncompatible

@CheckForNull

Exceptions

ClassCastException:

if the cause cannot be cast to the expected type. The ClassCastException's cause is throwable.

Since

22.0

Returns the innermost cause of throwable. The first throwable in a chain provides context from when the error or exception was initially detected. Example usage:

assertEquals("Unable to assign a customer id", Throwables.getRootCause(e).getMessage());

Exceptions

IllegalArgumentException:

if there is a loop in the causal chain

Returns a string containing the result of toString(), followed by the full, recursive stack trace of throwable. Note that you probably should not be parsing the resulting string; if you need programmatic access to the stack frames, you can call Throwable#getStackTrace().

Annotations

@GwtIncompatible

Returns the stack trace of throwable, possibly providing slower iteration over the full trace but faster iteration over parts of the trace. Here, "slower" and "faster" are defined in comparison to the normal way to access the stack trace, throwable.getStackTrace(). Note, however, that this method's special implementation is not available for all platforms and configurations. If that implementation is unavailable, this method falls back to getStackTrace. Callers that require the special implementation can check its availability with lazyStackTraceIsLazy().

The expected (but not guaranteed) performance of the special implementation differs from getStackTrace in one main way: The lazyStackTrace call itself returns quickly by delaying the per-stack-frame work until each element is accessed. Roughly speaking:

• getStackTrace takes stackSize time to return but then negligible time to retrieve each element of the returned list.
• lazyStackTrace takes negligible time to return but then 1/stackSize time to retrieve each element of the returned list (probably slightly more than 1/stackSize).

Annotations

@Deprecated

@J2ktIncompatible

@GwtIncompatible

Since

19.0

Returns whether lazyStackTrace will use the special implementation described in its documentation.

Annotations

@Deprecated

@J2ktIncompatible

@GwtIncompatible

Since

19.0

Propagates throwable as-is if it is an instance of RuntimeException or Error, or else as a last resort, wraps it in a RuntimeException and then propagates.

This method always throws an exception. The RuntimeException return type allows client code to signal to the compiler that statements after the call are unreachable. Example usage:

T doSomething() {
  try {
    return someMethodThatCouldThrowAnything();
  } catch (IKnowWhatToDoWithThisException e) {
    return handle(e);
  } catch (Throwable t) {
    throw Throwables.propagate(t);
  }
}

Parameters

throwable:Throwable

the Throwable to propagate

Returns:RuntimeException

nothing will ever be returned; this return type is only for your convenience, as illustrated in the example above

Annotations

@CanIgnoreReturnValue

@J2ktIncompatible

@GwtIncompatible

@Deprecated

Propagates throwable exactly as-is, if and only if it is an instance of declaredType. Example usage:

try {
  someMethodThatCouldThrowAnything();
} catch (IKnowWhatToDoWithThisException e) {
  handle(e);
} catch (Throwable t) {
  Throwables.propagateIfInstanceOf(t, IOException.class);
  Throwables.propagateIfInstanceOf(t, SQLException.class);
  throw Throwables.propagate(t);
}

Annotations

@Deprecated

@J2ktIncompatible

@GwtIncompatible

Propagates throwable exactly as-is, if and only if it is an instance of RuntimeException or Error. Example usage:

try {
  someMethodThatCouldThrowAnything();
} catch (IKnowWhatToDoWithThisException e) {
  handle(e);
} catch (Throwable t) {
  Throwables.propagateIfPossible(t);
  throw new RuntimeException("unexpected", t);
}

Annotations

@Deprecated

@J2ktIncompatible

@GwtIncompatible

Propagates throwable exactly as-is, if and only if it is an instance of RuntimeException, Error, or declaredType. Example usage:

try {
  someMethodThatCouldThrowAnything();
} catch (IKnowWhatToDoWithThisException e) {
  handle(e);
} catch (Throwable t) {
  Throwables.propagateIfPossible(t, OtherException.class);
  throw new RuntimeException("unexpected", t);
}

Parameters

throwable:Throwable

the Throwable to possibly propagate

declaredType:Class<X>

the single checked exception type declared by the calling method

Annotations

@J2ktIncompatible

@GwtIncompatible

Propagates throwable exactly as-is, if and only if it is an instance of RuntimeException, Error, declaredType1, or declaredType2. In the unlikely case that you have three or more declared checked exception types, you can handle them all by invoking these methods repeatedly. See usage example in propagateIfPossible(Throwable, Class).

Parameters

throwable:Throwable

the Throwable to possibly propagate

declaredType1:Class<X1>

any checked exception type declared by the calling method

declaredType2:Class<X2>

any other checked exception type declared by the calling method

Annotations

@J2ktIncompatible

@GwtIncompatible

Throws throwable if it is an instance of declaredType. Example usage:

for (Foo foo : foos) {
  try {
    foo.bar();
  } catch (BarException | RuntimeException | Error t) {
    failure = t;
  }
}
if (failure != null) {
  throwIfInstanceOf(failure, BarException.class);
  throwIfUnchecked(failure);
  throw new AssertionError(failure);
}

Annotations

@J2ktIncompatible

@GwtIncompatible

Since

20.0

Throws throwable if it is a RuntimeException or Error. Example usage:

for (Foo foo : foos) {
  try {
    foo.bar();
  } catch (RuntimeException | Error t) {
    failure = t;
  }
}
if (failure != null) {
  throwIfUnchecked(failure);
  throw new AssertionError(failure);
}

Since

20.0