Exceptions with deep causes. JRuby only shows the latest level, i.e. 'Exception on level 8' without any insight into the deeper causes.

nested_exceptions.rb

require 'java'

$CLASSPATH << File.expand_path('..', __FILE__)
Java::NestedExceptionTest.new.throw_nested_exceptions 8

NestedExceptionTest.java

public class NestedExceptionTest {

    public void throwNestedExceptions(int n) {
        if (n > 0) {
            try {
              throwNestedExceptions(n-1);
            } catch (Exception e) {
                throw new RuntimeException("Exception on level " + n, e);
            }
        } else {
            throw new RuntimeException("Root cause!");
        }
    }

    public static void main(String[] ignored) {
        new NestedExceptionTest().throwNestedExceptions(8);
    }

}

I don't think Ruby can throw nested exceptions; I believe JRuby mimics this behavior.