Security Exception While Running TestNG test in Eclipse juno

i am getting below error while trying to run testng in eclipse juno

Exception in thread "main" java.lang.NoSuchMethodError: org.testng.internal.Utils.defaultIfStringEmpty(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String; at org.testng.remote.AbstractRemoteTestNG.setHost(AbstractRemoteTestNG.java:59) at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:137) at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:57)

Plugin:6.9.12 testng jar:6.8.5 IDE:Eclipse Juno