java.util.ConcurrentModificationException

java.util.ConcurrentModificationException

with the testng also im getting same error, can you please let us know which version of the jar and how to achieve parallel execution with testNG

error
java.util.ConcurrentModificationException
at test.com.t.social.A.es_(A.java:1049)

Results :

Failed tests:
AA.es_:1049 » ConcurrentModification

Tests run: 260, Failures: 1, Errors: 0, Skipped: 0

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 55:11 min
[INFO] Finished at: 2017-03-10T10:50:25-05:00
[INFO] Final Memory: 22M/370M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.19.1:test (default-test) on project bot: There are test failures.
[ERROR]
[ERROR] Please refer to svalidation/target/surefire-reports for the individual test results.
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException