CODEWITHSUNDEEP
javakerneljupyter-notebookjupytersci-java
Norman Kong
Norman Kong

Reputation: 11

Error running a simple script in a jupyter notebook with SciJava

I am a complete beginner so please have patience. I am trying to run this script:

import java.util.Scanner;

public class Echo {

    public static void main(String[] args) {
        String line;
        Scanner in = new Scanner(System.in); 

        System.out.print("Type something: ");
        line = in.nextLine();
        System.out.println("You said: " + line);

    }
}

in my Jupyter kernel with SciJava, but I get this error:

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Script6.groovy: 7: expecting '}', found 'in' @ line 7, column 17.
           Scanner in = new Scanner(System.in); 
                   ^

1 error

    at org.codehaus.groovy.control.ErrorCollector.failIfErrors(ErrorCollector.java:310)
    at org.codehaus.groovy.control.ErrorCollector.addFatalError(ErrorCollector.java:150)
    at org.codehaus.groovy.control.ErrorCollector.addError(ErrorCollector.java:120)
    at org.codehaus.groovy.control.ErrorCollector.addError(ErrorCollector.java:132)
    at org.codehaus.groovy.control.SourceUnit.addError(SourceUnit.java:350)
    at org.codehaus.groovy.antlr.AntlrParserPlugin.transformCSTIntoAST(AntlrParserPlugin.java:144)
    at org.codehaus.groovy.antlr.AntlrParserPlugin.parseCST(AntlrParserPlugin.java:110)
    at org.codehaus.groovy.control.SourceUnit.parse(SourceUnit.java:234)
    at org.codehaus.groovy.control.CompilationUnit$1.call(CompilationUnit.java:168)
    at org.codehaus.groovy.control.CompilationUnit.applyToSourceUnits(CompilationUnit.java:943)
    at org.codehaus.groovy.control.CompilationUnit.doPhaseOperation(CompilationUnit.java:605)
    at org.codehaus.groovy.control.CompilationUnit.processPhaseOperations(CompilationUnit.java:581)
    at org.codehaus.groovy.control.CompilationUnit.compile(CompilationUnit.java:558)
    at groovy.lang.GroovyClassLoader.doParseClass(GroovyClassLoader.java:298)
    at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:268)
    at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:254)
    at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:250)
    at org.scijava.plugins.scripting.groovy.GroovyScriptEngine.getScriptClass(GroovyScriptEngine.java:319)
    at org.scijava.plugins.scripting.groovy.GroovyScriptEngine.eval(GroovyScriptEngine.java:122)
    at javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:264)
    at org.scijava.script.ScriptModule.run(ScriptModule.java:160)
    at org.scijava.module.ModuleRunner.run(ModuleRunner.java:168)
    at org.scijava.jupyter.kernel.evaluator.Worker.run(Worker.java:108)
    at org.scijava.thread.DefaultThreadService$2.run(DefaultThreadService.java:221)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

I tried to run the program through a script in my command terminal and it worked. To add, I have run other simple scripts before in this kernel but for some reason this one does not work.

If need be, please refer to the screenshot attached.

I am on macOS Mojave.

Thank you in advance!

Upvotes: 1

Views: 241

Answers (1)

SpencerPark
SpencerPark

Reputation: 3506

SciJava is a polyglot kernel which means it supports many different languages.

The README and notebook linking to the supported languages suggests that java is supported but the default is Groovy:

Some of the supported languages are Groovy (default), Python, Beanshell, Clojure, Java, Javascript, Ruby and Scala.

Although https://github.com/scijava/scijava-jupyter-kernel/issues/80 suggests java it is not operational.

Groovy is not java. It is fairly compatible but there are differences one of which you have found. in is a keyword in groovy and cannot be used as a variable name (see section 13).

The below is the same program in valid groovy:

import java.util.Scanner;

public class Echo {

    public static void main(String[] args) {
        String line;
        Scanner input = new Scanner(System.in); 

        System.out.print("Type something: ");
        line = input.nextLine();
        System.out.println("You said: " + line);

    }
}

Although this leads to the next issue that stdin is not supported https://github.com/scijava/scijava-jupyter-kernel/issues/96 but hopefully the answer so far untangles the error message you are originally getting.

Upvotes: 1

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