JavaAccess | R Documentation |
The $
operator for jobjRef
Java object references provides convenience access to object attributes and calling Java methods.
## S3 method for class 'jobjRef'
.DollarNames(x, pattern = "" )
## S3 method for class 'jarrayRef'
.DollarNames(x, pattern = "" )
## S3 method for class 'jrectRef'
.DollarNames(x, pattern = "" )
## S3 method for class 'jclassName'
.DollarNames(x, pattern = "" )
x |
object to complete |
pattern |
pattern |
rJava provides two levels of API: low-level JNI-API in the form of .jcall
function and high-level reflection API based on the $
operator. The former is very fast, but inflexible. The latter is a convenient way to use Java-like programming at the cost of performance. The reflection API is build around the $
operator on jobjRef-class
objects that allows to access Java attributes and call object methods.
$
returns either the value of the attribute or calls a method, depending on which name matches first.
$<-
assigns a value to the corresponding Java attribute.
names
and .DollarNames
returns all fields and methods associated with the object.
Method names are followed by (
or ()
depending on arity.
This use of names is mainly useful for code completion, it is not intended to be used programmatically.
This is just a convenience API. Internally all calls are mapped into .jcall
calls, therefore the calling conventions and returning objects use the same rules. For time-critical Java calls .jcall
should be used directly.
$
signature(x = "jobjRef")
: ...
$
signature(x = "jclassName")
: ...
$<-
signature(x = "jobjRef")
: ...
$<-
signature(x = "jclassName")
: ...
names
signature(x = "jobjRef")
: ...
names
signature(x = "jarrayRef")
: ...
names
signature(x = "jrectRef")
: ...
names
signature(x = "jclassName")
: ...
J
, .jcall
, .jnew
, jobjRef-class
v <- new(J("java.lang.String"), "Hello World!")
v$length()
v$indexOf("World")
names(v)
J("java.lang.String")$valueOf(10)
Double <- J("java.lang.Double")
# the class pseudo field - instance of Class for the associated class
# similar to java Double.class
Double$class
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