jcastToArray: Ensures that a given object is an array reference

In rJava: Low-Level R to Java Interface

Ensures that a given object is an array reference

Description

.jcastToArray takes a Java object reference of any kind and returns Java array reference if the given object is a reference to an array.

Usage

.jcastToArray(obj, signature=NULL, class="", quiet=FALSE)

Arguments

obj	Java object reference to cast or a scalar vector
signature	array signature in JNI notation (e.g. "[I" for an array of integers). If set to NULL (the default), the signature is automatically determined from the object's class.
class	force the result to pose as a particular Java class. This has the same effect as using .jcast on the result and is provided for convenience only.
quiet	if set to TRUE, no failures are reported and the original object is returned unmodified.

Details

Sometimes a result of a method is by definition of the class java.lang.Object, but the actual referenced object may be an array. In that case the method returns a Java object reference instead of an array reference. In order to obtain an array reference, it is necessary to cast such an object to an array reference - this is done using the above .jcastToArray function.

The input is an object reference that points to an array. Usually the signature should be left at NULL such that it is determined from the object's class. This is also a check, because if the object's class is not an array, then the functions fails either with an error (when quiet=FALSE) or by returning the original object (when quiet=TRUE). If the signature is set to anything else, it is not verified and the array reference is always created, even if it may be invalid and unusable.

For convenience .jcastToArray also accepts non-references in which case it simply calls .jarray, ignoring all other parameters.

Value

Returns a Java array reference (jarrayRef) on success. If quiet is TRUE then the result can also be the original object in the case of failure.

Examples

## Not run: 
a <- .jarray(1:10)
print(a)
# let's create an array containing the array
aa <- .jarray(list(a))
print(aa)
ba <- .jevalArray(aa)[[1]]
# it is NOT the inverse, because .jarray works on a list of objects
print(ba)
# so we need to cast the object into an array
b <- .jcastToArray(ba)
# only now a and b are the same array reference
print(b)
# for convenience .jcastToArray behaves like .jarray for non-references
print(.jcastToArray(1:10/2))

## End(Not run)

rJava documentation built on May 29, 2024, 5:26 a.m.