Java Reference
In-Depth Information
cause is created by invoking the
Throwable(Throwable cause)
or
Throw-
able(String message, Throwable cause)
constructor, which invoke the
initCause()
methodtostorethecause.Ifyoudonotcalleitherconstructor,youcan
alternativelycall
initCause()
directly,butmustdosoimmediatelyaftercreatingthe
throwable. Call the
getCause()
method to return the cause.
When one exception causes another exception, the first exception is usually caught
and then the second exception is thrown in response. In other words, there is a causal
connectionbetweenthetwoexceptions.Incontrast,therearesituationswheretwoinde-
pendentexceptionscanbethrowninsiblingcodeblocks;forexample,inthetryblock
ofatry-with-resourcesstatement(discussedlaterinthischapter)andthecompiler-gen-
eratedfinallyblockthatclosestheresource.Inthesesituations,onlyoneofthethrown
exceptions can be propagated.
In the try-with-resources statement, when there are two such exceptions, the excep-
tionoriginatingfromthetryblockispropagatedandtheexceptionfromthefinallyblock
isadded(viathe
addSuppressed()
method)tothelistofexceptions
suppressed
by
theexceptionfromthetryblock.Asanexceptionunwindsthestack,itcanaccumulate
multiplesuppressedexceptions.Anarrayofthesuppressedexpressionscanberetrieved
by calling
getSuppressed()
.
When an exception is thrown, it leaves behind a stack of unfinished method calls.
Throwable
'sconstructorscall
fillInStackTrace()
torecordthis
stack trace
in-
formation, which is output by calling
printStackTrace()
.
The
getStackTrace()
method provides programmatic access to the stack trace
byreturningthisinformationasanarrayof
java.lang.StackTraceElement
in-
stances - each instance represents one stack entry.
StackTraceElement
provides
methods to return stack trace information. For example,
String getMeth-
odName()
returns the name of an unfinished method.
The
setStackTrace()
method is designed for use by Remote Procedure Call
(RPC) frameworks (RPC is briefly discussed in
Chapter 11
) and other advanced sys-
tems, allowing the client to override the default stack trace that is generated by
fillInStackTrace()
when a throwable is constructed, or deserialized when a
Exceptfor
Throwable(String message, Throwable cause, boolean
enableSuppression, boolean writableStackTrace)
, each
Throw-
able
constructor always treats suppression as being enabled, and always calls
fillInStackTrace()
. In contrast, this constructor lets you disable suppression
bypassing
false
to
enableSuppression
,andprevent
fillInStackTrace()
