Class Throwables
- java.lang.Object
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- com.google.common.base.Throwables
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@GwtCompatible(emulated=true) public final class Throwables extends Object
Static utility methods pertaining to instances ofThrowable
.See the Guava User Guide entry on Throwables.
- Since:
- 1.0
- Author:
- Kevin Bourrillion, Ben Yu
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Method Summary
All Methods Static Methods Concrete Methods Deprecated Methods Modifier and Type Method Description static List<Throwable>
getCausalChain(Throwable throwable)
Gets aThrowable
cause chain as a list.static <X extends Throwable>
@Nullable XgetCauseAs(Throwable throwable, Class<X> expectedCauseType)
Returnsthrowable
's cause, cast toexpectedCauseType
.static Throwable
getRootCause(Throwable throwable)
Returns the innermost cause ofthrowable
.static String
getStackTraceAsString(Throwable throwable)
Returns a string containing the result oftoString()
, followed by the full, recursive stack trace ofthrowable
.static List<StackTraceElement>
lazyStackTrace(Throwable throwable)
Deprecated.This method is equivalent toThrowable.getStackTrace()
on JDK versions past JDK 8 and on all Android versions.static boolean
lazyStackTraceIsLazy()
Deprecated.This method always returns false on JDK versions past JDK 8 and on all Android versions.static RuntimeException
propagate(Throwable throwable)
Deprecated.To preserve behavior, usethrow e
orthrow new RuntimeException(e)
directly, or use a combination ofthrowIfUnchecked(java.lang.Throwable)
andthrow new RuntimeException(e)
.static <X extends Throwable>
voidpropagateIfInstanceOf(@Nullable Throwable throwable, Class<X> declaredType)
Deprecated.UsethrowIfInstanceOf(java.lang.Throwable, java.lang.Class<X>)
, which has the same behavior but rejectsnull
.static void
propagateIfPossible(@Nullable Throwable throwable)
Deprecated.UsethrowIfUnchecked(java.lang.Throwable)
, which has the same behavior but rejectsnull
.static <X extends Throwable>
voidpropagateIfPossible(@Nullable Throwable throwable, Class<X> declaredType)
Deprecated.Use a combination ofthrowIfInstanceOf(java.lang.Throwable, java.lang.Class<X>)
andthrowIfUnchecked(java.lang.Throwable)
, which togther provide the same behavior except that they rejectnull
.static <X1 extends Throwable,X2 extends Throwable>
voidpropagateIfPossible(@Nullable Throwable throwable, Class<X1> declaredType1, Class<X2> declaredType2)
Deprecated.Use a combination of two calls tothrowIfInstanceOf(java.lang.Throwable, java.lang.Class<X>)
and one call tothrowIfUnchecked(java.lang.Throwable)
, which togther provide the same behavior except that they rejectnull
.static <X extends Throwable>
voidthrowIfInstanceOf(Throwable throwable, Class<X> declaredType)
Throwsthrowable
if it is an instance ofdeclaredType
.static void
throwIfUnchecked(Throwable throwable)
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Method Detail
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throwIfInstanceOf
@GwtIncompatible public static <X extends Throwable> void throwIfInstanceOf(Throwable throwable, Class<X> declaredType) throws X extends Throwable
Throwsthrowable
if it is an instance ofdeclaredType
. 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); }
- Throws:
X extends Throwable
- Since:
- 20.0
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propagateIfInstanceOf
@Deprecated @GwtIncompatible public static <X extends Throwable> void propagateIfInstanceOf(@Nullable Throwable throwable, Class<X> declaredType) throws X extends Throwable
Deprecated.UsethrowIfInstanceOf(java.lang.Throwable, java.lang.Class<X>)
, which has the same behavior but rejectsnull
.Propagatesthrowable
exactly as-is, if and only if it is an instance ofdeclaredType
. 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); }
- Throws:
X extends Throwable
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throwIfUnchecked
public static void throwIfUnchecked(Throwable throwable)
Throwsthrowable
if it is aRuntimeException
orError
. 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
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propagateIfPossible
@Deprecated @GwtIncompatible public static void propagateIfPossible(@Nullable Throwable throwable)
Deprecated.UsethrowIfUnchecked(java.lang.Throwable)
, which has the same behavior but rejectsnull
.
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propagateIfPossible
@Deprecated @GwtIncompatible public static <X extends Throwable> void propagateIfPossible(@Nullable Throwable throwable, Class<X> declaredType) throws X extends Throwable
Deprecated.Use a combination ofthrowIfInstanceOf(java.lang.Throwable, java.lang.Class<X>)
andthrowIfUnchecked(java.lang.Throwable)
, which togther provide the same behavior except that they rejectnull
.Propagatesthrowable
exactly as-is, if and only if it is an instance ofRuntimeException
,Error
, ordeclaredType
.Discouraged in favor of calling
throwIfInstanceOf(java.lang.Throwable, java.lang.Class<X>)
andthrowIfUnchecked(java.lang.Throwable)
.- Parameters:
throwable
- the Throwable to possibly propagatedeclaredType
- the single checked exception type declared by the calling method- Throws:
X extends Throwable
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propagateIfPossible
@Deprecated @GwtIncompatible public static <X1 extends Throwable,X2 extends Throwable> void propagateIfPossible(@Nullable Throwable throwable, Class<X1> declaredType1, Class<X2> declaredType2) throws X1 extends Throwable, X2 extends Throwable
Deprecated.Use a combination of two calls tothrowIfInstanceOf(java.lang.Throwable, java.lang.Class<X>)
and one call tothrowIfUnchecked(java.lang.Throwable)
, which togther provide the same behavior except that they rejectnull
.Propagatesthrowable
exactly as-is, if and only if it is an instance ofRuntimeException
,Error
,declaredType1
, ordeclaredType2
.- Parameters:
throwable
- the Throwable to possibly propagatedeclaredType1
- any checked exception type declared by the calling methoddeclaredType2
- any other checked exception type declared by the calling method- Throws:
X1 extends Throwable
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propagate
@CanIgnoreReturnValue @GwtIncompatible @Deprecated public static RuntimeException propagate(Throwable throwable)
Deprecated.To preserve behavior, usethrow e
orthrow new RuntimeException(e)
directly, or use a combination ofthrowIfUnchecked(java.lang.Throwable)
andthrow new RuntimeException(e)
. But consider whether users would be better off if your API threw a different type of exception. For background on the deprecation, read Why we deprecatedThrowables.propagate
.Propagatesthrowable
as-is if it is an instance ofRuntimeException
orError
, or else as a last resort, wraps it in aRuntimeException
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
- the Throwable to propagate- Returns:
- nothing will ever be returned; this return type is only for your convenience, as illustrated in the example above
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getRootCause
public static Throwable getRootCause(Throwable throwable)
Returns the innermost cause ofthrowable
. 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());
- Throws:
IllegalArgumentException
- if there is a loop in the causal chain
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getCausalChain
public static List<Throwable> getCausalChain(Throwable throwable)
Gets aThrowable
cause chain as a list. The first entry in the list will bethrowable
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
- the non-nullThrowable
to extract causes from- Returns:
- an unmodifiable list containing the cause chain starting with
throwable
- Throws:
IllegalArgumentException
- if there is a loop in the causal chain
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getCauseAs
@GwtIncompatible public static <X extends Throwable> @Nullable X getCauseAs(Throwable throwable, Class<X> expectedCauseType)
Returnsthrowable
's cause, cast toexpectedCauseType
.Prefer this method instead of manually casting an exception's cause. For example,
(IOException) e.getCause()
throws aClassCastException
that discards the original exceptione
if the cause is not anIOException
, butThrowables.getCauseAs(e, IOException.class)
keepse
as theClassCastException
's cause.- Throws:
ClassCastException
- if the cause cannot be cast to the expected type. TheClassCastException
's cause isthrowable
.- Since:
- 22.0
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getStackTraceAsString
@GwtIncompatible public static String getStackTraceAsString(Throwable throwable)
Returns a string containing the result oftoString()
, followed by the full, recursive stack trace ofthrowable
. Note that you probably should not be parsing the resulting string; if you need programmatic access to the stack frames, you can callThrowable.getStackTrace()
.
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lazyStackTrace
@Deprecated @GwtIncompatible public static List<StackTraceElement> lazyStackTrace(Throwable throwable)
Deprecated.This method is equivalent toThrowable.getStackTrace()
on JDK versions past JDK 8 and on all Android versions. UseThrowable.getStackTrace()
directly, or where possible use thejava.lang.StackWalker.walk
method introduced in JDK 9.Returns the stack trace ofthrowable
, 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 togetStackTrace
. Callers that require the special implementation can check its availability withlazyStackTraceIsLazy()
.The expected (but not guaranteed) performance of the special implementation differs from
getStackTrace
in one main way: ThelazyStackTrace
call itself returns quickly by delaying the per-stack-frame work until each element is accessed. Roughly speaking:getStackTrace
takesstackSize
time to return but then negligible time to retrieve each element of the returned list.lazyStackTrace
takes negligible time to return but then1/stackSize
time to retrieve each element of the returned list (probably slightly more than1/stackSize
).
Note: The special implementation does not respect calls to
throwable.setStackTrace
. Instead, it always reflects the original stack trace from the exception's creation.- Since:
- 19.0
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lazyStackTraceIsLazy
@Deprecated @GwtIncompatible public static boolean lazyStackTraceIsLazy()
Deprecated.This method always returns false on JDK versions past JDK 8 and on all Android versions.Returns whetherlazyStackTrace(java.lang.Throwable)
will use the special implementation described in its documentation.- Since:
- 19.0
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