rJava (version 1.0-11)

with.jobjRef: with and within methods for Java objects and class names

Description

Convenience wrapper that allow calling methods of Java object and classes from within the object (or class).

Usage

# S3 method for jobjRef
with(data, expr, ...)
# S3 method for jobjRef
within(data, expr, ...)
# S3 method for jarrayRef
with(data, expr, ...)
# S3 method for jarrayRef
within(data, expr, ...)
# S3 method for jclassName
with(data, expr, ...)
# S3 method for jclassName
within(data, expr, ...)

Value

with returns the value of the expression and

within returns the data argument

Arguments

data

A Java object reference or a java class name. See J

expr

R expression to evaluate

...

ignored

Author

Romain Francois <[e-mail]>

Details

The expression is evaluated in an environment that contains a mapping between the public fields and methods of the object.

The methods of the object are mapped to standard R functions in the environment. In case of classes, only static methods are used.

The fields of the object are mapped to active bindings (see makeActiveBinding) so that they can be accessed and modified from within the environment. For classes, only static fields are used.

References

the java.lang.reflect package: https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/package-summary.html

Examples

.jinit()

if (!nzchar(Sys.getenv("NOAWT"))) {
  p <- .jnew( "java/awt/Point", 0L, 0L )
  with( p, {
	# x and y and now 0
	move( 10L, 10L )
	# x and y are now 10
	x <- x + y
  } )

  f <- within( .jnew( "javax/swing/JFrame" ) , {
	layout <- .jnew( "java/awt/BorderLayout" )
	setLayout( layout )
	add( .jnew( "javax/swing/JLabel", "north" ), layout$NORTH )
	add( .jnew( "javax/swing/JLabel", "south" ), layout$SOUTH )
	add( .jnew( "javax/swing/JLabel", "west" ), layout$WEST )
	add( .jnew( "javax/swing/JLabel", "east" ), layout$EAST )
	setSize( .jnew( "java/awt/Dimension", 400L, 400L ) )
	setVisible( TRUE )
  } )
}

Double <- J("java.lang.Double")
with( Double, MIN_VALUE )
with( Double, parseDouble( "10.2" ) )

if (FALSE) {
# inner class example

HashMap <- J("java.util.HashMap")
with( HashMap, new( SimpleEntry, "key", "value" ) )
with( HashMap, SimpleEntry )
}

with( J("java.lang.System"), getProperty("java.home") )

# \dontshow{
stopifnot( with( Double, parseDouble("10.0") ) == 10.0 )
d <- new( Double, "10.0") 
stopifnot( with( d, doubleValue() ) == 10.0 )
# }