\name{Exceptions}

\alias{Exceptions}

\alias{$.Throwable}

\alias{$<-.Throwable}

\title{Exception handling}

\description{R handling of java exception}

\usage{

\S3method{$}{Throwable}(x, name )

\S3method{$}{Throwable}(x, name ) <- value

}

\arguments{

\item{x}{condition}

\item{name}{...}

\item{value}{...}

}

\details{

Java exceptions are mapped to R conditions that are relayed by the

\code{\link{stop}} function.

The R condition contains the actual exception object as the

\code{jobj} item.

The class name of the R condition is made of a vector

of simple java class names, the class names without their package

path. This allows the R code to use direct handlers similar to

direct exception handlers in java. See the example below.

}

\examples{

\dontshow{.jinit()}

Integer <- J("java.lang.Integer")

tryCatch( Integer$parseInt( "10.." ), NumberFormatException = function(e){

e$jobj$printStackTrace()

} )

# the dollar method is also implemented for Throwable conditions,

# so that syntactic sugar can be used on condition objects

# however, in the example below e is __not__ a jobjRef object reference

tryCatch( Integer$parseInt( "10.." ), NumberFormatException = function(e){

e$printStackTrace()

} )

\dontshow{

tryCatch( Integer$parseInt( "10.." ), NumberFormatException = function(e){

classes <- class( e )

stopifnot( "NumberFormatException" \%in\% classes )

stopifnot( "Exception" \%in\% classes )

stopifnot( "Object" \%in\% classes )

stopifnot( "error" \%in\% classes )

stopifnot( "condition" \%in\% classes )

} )

}

}