Develop Reference

VS code unable to create new cell while using iJAVA that is build on jshell?

I am just a beginner :) Can any one help me out??
When I click the plus sign to create a new cell in a workbook I get an error. The new cell isn't created and I see this error message in a larger than usual font.
The error message survives a restart of the kernel.
The error is gone after I restart VSCode.
The error is also gone after I save / close the file and re-open it.
code
System.out.print("hello jshell");
and then i hit alt + enter
output
hello jshell
TypeError: Cannot read property 'charAt' of undefined at
in t
in div
in t
in div
in t
in div
in t
in div
in div
in div
in div
in div
in div
in t
in h
in t
in div
in div
in div
in t
in main
in div
in t
in h
in f
I am using
VS-code version : 1.51.1
jupyter core : 4.6.3
jupyter-notebook : 6.1.5
qtconsole : 4.7.7
ipython : 7.18.1
ipykernel : 5.3.4
jupyter client : 6.1.7
jshell : 15.0.1
out put screen shot

I've added the java to Jupyter Kernel and with many tests conducted, it's an issue in VS Code:
There're many similar issues posted in GitHub and now, this function is solved in VS Code Insiders but still not in VS Code:
You can install VS Code Insider, but it may not that stable, after all it's the beta-version of VS Code. In another way, you can turn to JupyterLab, try it in browser or install it.

Did Matlab 2017a change how it imports external java classes?

I'm calling PDFBox from Matlab to figure out how many pages there are in a PDF. Everything works great with Matlba 2016b and prior. I can import the library and load a PDF without a problem:
import org.apache.pdfbox.pdmodel.PDDocument;
pdfFile = PDDocument.load(filename);
When I run the same thing in 2017a, I get the following error:
No method 'load' with matching signature found for class
'org.apache.pdfbox.pdmodel.PDDocument'.
I can change the line after the import so that the function signature matches:
jFilename = java.lang.String(filename);
pdfFile = PDDocument.load(jFilename.getBytes());
However, this causes PDFBox to have problems when I call load:
Java exception occurred:
java.io.IOException: Error: End-of-File, expected line
at org.apache.pdfbox.pdfparser.BaseParser.readLine(BaseParser.java:1111)
at org.apache.pdfbox.pdfparser.COSParser.parseHeader(COSParser.java:1874)
at org.apache.pdfbox.pdfparser.COSParser.parsePDFHeader(COSParser.java:1853)
at org.apache.pdfbox.pdfparser.PDFParser.parse(PDFParser.java:242)
at org.apache.pdfbox.pdmodel.PDDocument.load(PDDocument.java:1093)
at org.apache.pdfbox.pdmodel.PDDocument.load(PDDocument.java:1071)
at org.apache.pdfbox.pdmodel.PDDocument.load(PDDocument.java:1053)
at org.apache.pdfbox.pdmodel.PDDocument.load(PDDocument.java:1038)
This error seems to occur regardless of the PDF I'm trying to load. I'm getting the same exception with PDFBox 1.8.10 and 2.0.6.
I'm left with 2 questions:
Did Matlab 2017a change how it passes strings to Java? I didn't see anything in the release notes about this.
What could be causing the PDFBox error? Matlab is still on Java 1.7 in 2017a so I wouldn't think there should be any difference in how PDFBox works.

It seems like the method you are calling is from PDDocument version 1.8.11
In the latest version, PDDocument version 2.0.2 the method signature for accepting a file name no longer exists.
Change your code to the following, and it should work.
pdfFile = PDDocument.load(java.io.File(filename));

Error writing xlsx in R: Could not initialize class sun.java2d.Disposer

I'm using the xlsx package to write Excel files in R:
addPicture('trend_indirect.png' ,sheet1)
addDataFrame(df.ssis_duplmonth ,sheet1, startRow=22)
addDataFrame(df.ssis_dupltrans ,sheet1, startRow=35)
addDataFrame(df.ssis_duplmonth_dir, sheet2, startRow=22)
addDataFrame(df.ssis_dupltrans_dir, sheet2, startRow=55)
saveWorkbook(wb, file="SSIS_import_controls.xlsx")
At this point I get the following error:
> addDataFrame(df.ssis_duplmonth ,sheet1, startRow=22)
Error in .jcall("RJavaTools", "Z", "hasField", .jcast(x, "java/lang/Object"), :
java.lang.NoClassDefFoundError: Could not initialize class sun.java2d.Disposer
R version 2.15.2, 32bit.
Thanks
Edit: I can't really make it reproducible as probably the issue is in my settings but I get the error when I run this:
library('xlsx')
df.test <- iris[1:5, ]
wb <- createWorkbook()
sheet1 <- createSheet(wb, 'Indirect Sales')
addPicture('trend_indirect.png' ,sheet1)
addDataFrame(df.test ,sheet1, startRow=22)
saveWorkbook(wb, file="stack_test.xlsx")
The image is just a simple ggplot graph saved in png. Thanks

Try installing libxtst. That solved a similar problem for me.
I also installed fontconfig and libcups in the course of solving my issue, in case it wasn't libxtst that fixed it.

I was with the same exception but running a Java program using Ubuntu 12.
I've installed libxtst6 and add this java parameter to my JAVA_OPTS variable: -Djava.awt.headless=true
Then it works fine.

How to apply a patch

I have this patch code which i downloaded from a web article (Calling Matlab from Java).
http://www.cs.virginia.edu/~whitehouse/matlab/JavaMatlab.html
But I donot know how to apply it in my windowsXp running computer.
What I'm trying to do is call Matlab script file from java. I have found the necessary source codes and every thing but this mater is holding be back.
Any help is highly appreciated. Thank you.
Here's the patch code.
Index: MatlabControl.java
===================================================================
RCS file: /cvsroot/tinyos/tinyos-1.x/tools/java/net/tinyos/matlab/MatlabControl.java,v
retrieving revision 1.3
diff -u -r1.3 MatlabControl.java
--- MatlabControl.java 31 Mar 2004 18:43:50 -0000 1.3
+++ MatlabControl.java 16 Aug 2004 20:36:51 -0000
## -214,7 +214,8 ##
matlab.evalConsoleOutput(command);
}else{
- matlab.fevalConsoleOutput(command, args, 0, null);
+ // matlab.fevalConsoleOutput(command, args, 0, null);
+ matlab.fevalConsoleOutput(command, args);
}
} catch (Exception e) {
System.out.println(e.toString());

I'd download the standard UNIX patch tool and use:
patch -p0 <my_patch.diff

You need to apply that patch to the file MatlabControl.java. On Unix, you have the standard patch program to do that, but that ofcourse isn't normally present on Windows.
But looking at the patch file, it's very small and you could easily do the change by hand. Look at the patch file: The lines with a - in the left column must be removed. The lines with a + must be added.
So you must look in MatlabControl.java and remove this line:
matlab.fevalConsoleOutput(command, args, 0, null);
And add these lines:
// matlab.fevalConsoleOutput(command, args, 0, null);
matlab.fevalConsoleOutput(command, args);
In other words, it's a very small and simple change, you just have to remove the last two arguments to the method call to fevalConsoleOutput().
If you want the patch command (and lots of other Unix utilities) on Windows, you could download and install Cygwin.

If you use dev tools like Eclipse you can easily apply it as it is an option in the contextual menu (right click) go to Team - > Apply Patch. It should work.

This patch is so small, you can easily apply it by hand.
So simply open the file MatlabControl.java and change line 214 (the one prepended with -) to fit the lines prepended with +.
After that your code should look like:
else{
// matlab.fevalConsoleOutput(command, args, 0, null);
matlab.fevalConsoleOutput(command, args);
}

JMI (Java-to-Matlab Interface)'s Matlab class and its fevalConsoleOutput method are explained here: http://UndocumentedMatlab.com/blog/jmi-java-to-matlab-interface/

By Tortoise SVN, we can apply patch by following the below way. Click on Apply patch and browse the patch file.
Tortoise SVN

Problem validating against an XSD with Java5

I'm trying to validate an Atom feed with Java 5 (JRE 1.5.0 update 11). The code I have works without problem in Java 6, but fails when running in Java 5 with a
org.xml.sax.SAXParseException: src-resolve: Cannot resolve the name 'xml:base' to a(n) 'attribute declaration' component.
I think I remember reading something about the version of Xerces bundled with Java 5 having some problems with some schemas, but i cant find the workaround. Is it a known problem ? Do I have some error in my code ?
public static void validate() throws SAXException, IOException {
List<Source> schemas = new ArrayList<Source>();
schemas.add(new StreamSource(AtomValidator.class.getResourceAsStream("/atom.xsd")));
schemas.add(new StreamSource(AtomValidator.class.getResourceAsStream("/dc.xsd")));
// Lookup a factory for the W3C XML Schema language
SchemaFactory factory = SchemaFactory.newInstance("http://www.w3.org/2001/XMLSchema");
// Compile the schemas.
Schema schema = factory.newSchema(schemas.toArray(new Source[schemas.size()]));
Validator validator = schema.newValidator();
// load the file to validate
Source source = new StreamSource(AtomValidator.class.getResourceAsStream("/sample-feed.xml"));
// check the document
validator.validate(source);
}
Update : I tried the method below, but I still have the same problem if I use Xerces 2.9.0. I also tried adding xml.xsd to the list of schemas (as xml:base is defined in xml.xsd) but this time I have
Exception in thread "main" org.xml.sax.SAXParseException: schema_reference.4: Failed to read schema document 'null', because 1) could not find the document; 2) the document could not be read; 3) the root element of the document is not <xsd:schema>.
Update 2: I tried to configure a proxy with the VM arguments -Dhttp.proxyHost=<proxy.host.com> -Dhttp.proxyPort=8080 and now it works. I'll try to post a "real answer" from home.
and sorry, I cant reply as a comment : because of security reasons XHR is disabled from work ...

Indeed, people have been mentioning the Java 5 Sun provided SchemaFactory is giving troubles.
So: did you include Xerces in your project yourself?
After including Xerces, you need to ensure it is being used. If you like to hardcode it (well, as a minimal requirement you'd probably use some application properties file to enable and populate the following code):
String schemaFactoryProperty =
"javax.xml.validation.SchemaFactory:" + XMLConstants.W3C_XML_SCHEMA_NS_URI;
System.setProperty(schemaFactoryProperty,
"org.apache.xerces.jaxp.validation.XMLSchemaFactory");
SchemaFactory factory =
SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
Or, if you don't want to hardcode, or when your troublesome code would be in some 3rd party library that you cannot change, set it on the java command line or environment options. For example (on one line of course):
set JAVA_OPTS =
"-Djavax.xml.validation.SchemaFactory:http://www.w3.org/2001/XMLSchema
=org.apache.xerces.jaxp.validation.XMLSchemaFactory"
By the way: apart from the Sun included SchemaFactory implementation giving trouble (something like com.sun.org.apache.xerces.internal.jaxp.validation.xs.schemaFactoryImpl), it also seems that the "discovery" of non-JDK implementations fails in that version. If I understand correctly than, normally, just including Xerces would in fact make SchemaFactory#newInstance find that included library, and give it precedence over the Sun implementation. To my knowledge, that fails as well in Java 5, making the above configuration required.

I tried to configure a proxy with the VM arguments -Dhttp.proxyHost=<proxy.host.com> -Dhttp.proxyPort=8080 and now it works.
Ah, I didn't realize that xml.xsd is in fact the one referenced as http://www.w3.org/2001/xml.xsd or something like that. That should teach us to always show some XML and XSD fragments as well. ;-)
So, am I correct to assume that 1.) to fix the Java 5 issue, you still needed to include Xerces and set the system property, and that 2.) you did not have xml.xsd available locally?
Before you found your solution, did you happen to try using getResource rather than getResourceAsStream, to see if the exception would then have showed you some more details?
If you actually did have xml.xsd available (so: if getResource did in fact yield a URL) then I wonder what Xerces was trying to fetch from the internet then. Or maybe you did not add that schema to the list prior to adding your own schemas? The order is important: dependencies must be added first.
For whoever gets tot his question using the search: maybe using a custom EntityResolver could have indicated the source of the problem as well (if only writing something to the log and just returning null to tell Xerces to use the default behavior).

Hmmm, just read your "comment" -- editing does not alert people for new replies, so time to ask your boss for some iPhone or some other gadget that is connected to the net directly ;-)
Well, I assume you added:
schemas.add(
new StreamSource(AtomValidator.class.getResourceAsStream("/xml.xsd")));
If so, is xml.xsd actually to be found on the classpath then? I wonder if the getResourceAsStream did not yield null in your case, and how new StreamSource(null) would act then.
Even if getResourceAsStream did not yield null, the resulting StreamSource would still not know where it was loaded from, which may be a problem when trying to include references. So, what if you use the constructor StreamSource(String systemId) instead:
schemas.add(new StreamSource(AtomValidator.class.getResource("/atom.xsd")));
schemas.add(new StreamSource(AtomValidator.class.getResource("/dc.xsd")));
You might also use StreamSource(InputStream inputStream, String systemId), but I don't see any advantage over the above two lines. However, the documentation explains why passing the systemId in either of the 2 constructors seems good:
This constructor allows the systemID to be set in addition to the input stream, which allows relative URIs to be processed.
Likewise, setSystemId(String systemId) explains a bit:
The system identifier is optional if there is a byte stream or a character stream, but it is still useful to provide one, since the application can use it to resolve relative URIs and can include it in error messages and warnings (the parser will attempt to open a connection to the URI only if there is no byte stream or character stream specified).
If this doesn't work out, then maybe some custom error handler can give you more details:
ErrorHandlerImpl errorHandler = new ErrorHandlerImpl();
validator.setErrorHandler(errorHandler);
:
:
validator.validate(source);
if(errorHandler.hasErrors()){
LOG.error(errorHandler.getMessages());
throw new [..];
}
if(errorHandler.hasWarnings()){
LOG.warn(errorHandler.getMessages());
}
...using the following ErrorHandler to capture the validation errors and continue parsing as far as possible:
import org.xml.sax.helpers.DefaultHandler;
private class ErrorHandlerImpl extends DefaultHandler{
private String messages = "";
private boolean validationError = false;
private boolean validationWarning = false;
public void error(SAXParseException exception) throws SAXException{
messages += "Error: " + exception.getMessage() + "\n";
validationError = true;
}
public void fatalError(SAXParseException exception) throws SAXException{
messages += "Fatal: " + exception.getMessage();
validationError = true;
}
public void warning(SAXParseException exception) throws SAXException{
messages += "Warn: " + exception.getMessage();
validationWarning = true;
}
public boolean hasErrors(){
return validationError;
}
public boolean hasWarnings(){
return validationWarning;
}
public String getMessages(){
return messages;
}
}