Re: Accessing static members with J/Link

*To*: mathgroup at smc.vnet.net*Subject*: [mg110985] Re: Accessing static members with J/Link*From*: David Bailey <dave at removedbailey.co.uk>*Date*: Fri, 16 Jul 2010 05:15:35 -0400 (EDT)*References*: <i1mc8o$8v5$1@smc.vnet.net>

On 15/07/10 08:10, John_V wrote: > I'm trying to learn how to use J/Link, and I have run into an elementary > (I hope) problem when I try to access static methods and fields. For > example, the Java Math class has static fields for E and PI and a number > of static methods, abs() among them. Here's what happens when I try to > use them: > > My inputs: > > Needs["JLink`"] > InstallJava[] > myMathClass = LoadJavaClass["java.lang.Math"] > Fields[myMathClass] > pi = myMathClass`PI > myMathClass`abs[-5] > > /Mathematica/'s outputs: > > Out[2]= LinkObject[...] > > Out[3]= JavaClass[java.lang.Math,<> ] > > Out[4]//TableForm= > static final double E > static final double PI > > Out[5]= myMathClass`PI > > Out[6]= myMathClass`abs[-5] > > I believe the fact that Out[4] correctly lists java.lang.Math's static > fields means LoadJavaClass worked, but I expected Out[5] = 3.1415... and > Out[6] = 5. I thought this was a near verbatim transcription of the > examples in the "Calling Methods and Accessing Fields" part of the > J/Link user guide. What am I doing wrong? > > Thanks, > > John > After loading the relevant class, you should be able to access static members by using the full Java name with context marks instead of the periods: In[8]:= java`lang`Math`PI Out[8]= 3.14159 Note that although these appear like simple Mathematica variables, they have been setup with SetDelayed, so that evaluateing one accesses the corresponding variable in Java - to see this, type: ?java`lang`Math`PI David Bailey http://www.dbaileyconsultancy.co.uk