在控制台中抑制rjava错误输出

Question

How can I suppress the rJava output to the console in the following example?

library(rJava)
TC <- J("edu.cens.spatial.RTileController")
         dummy <- capture.output(suppressWarnings(suppressMessages(
res <- TC$getInstance(type="osm-bw")$getTileValues(4389,2691,13)
         )))

Despite capture.output , I still get the following in the console:

java.lang.NullPointerException
    at edu.cens.spatial.RTileController.getTileValues(RTileController.java:109)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at RJavaTools.invokeMethod(RJavaTools.java:386)

Edit : In pure R Console (without Rstudio), I get no messages (but I have to call library("OpenStreetMap") first). So this might be an Rstudio issue after all ... The question is now: how can I suppres Java output to the R console in Rstudio? Is it possible to do this when calling osmtile as outlined below?

PS1: It works for osm instead of osm-bw .
PS2: I came across this via

tile <- OpenStreetMap::osmtile(x=4389,y=2691,zoom=13,type="osm-bw")

Answer 1

In my case, something like this works - NullPointer message is suppressed:

> s <- .jcall(obj, returnSig="V", method="nullcall")
Error in .jcall(obj, returnSig = "V", method = "nullcall") :
  java.lang.NullPointerException: Exception
> suppressMessages(s <- .jcall(obj, returnSig="V", method="nullcall"))

To reproduce this code do following:

1. Create file (from within R)

    dir.create("utils") dir.create("target") cat('package utils; public class RUsingStringArray { public void nullcall() throws NullPointerException { throw new NullPointerException("Exception"); } public static void main(String [] arg) { RUsingStringArray obj = new RUsingStringArray(); obj.nullcall(); } }', file="utils/RUsingStringArray.java") 

2. Compile java code (in cmd / terminal, last line won't work on windows)

    javac -d target utils/*.java java -cp target utils/RUsingStringArray Exception in thread "main" java.lang.NullPointerException: Exception at utils.RUsingStringArray.nullcall(RUsingStringArray.java:19) at utils.RUsingStringArray.main(RUsingStringArray.java:24) export CLASSPATH=`pwd`/target 

3. Inside R

    library(rJava) .jinit("C:/path_to_folder/target") # leave empty if CLASSPATH was set obj <- .jnew("utils.RUsingStringArray") s <- .jcall(obj, returnSig="V", method="nullcall") suppressMessages(s <- .jcall(obj, returnSig="V", method="nullcall")) Error in .jcall(obj, returnSig = "V", method = "nullcall") : java.lang.NullPointerException: Exception