Encounter error

E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
Process: com.example.test, PID: 22838
java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:300)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
at java.util.concurrent.FutureTask.run(FutureTask.java:242)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:841)
Caused by: java.lang.VerifyError: net/sourceforge/jtds/jdbc/TdsCore
at net.sourceforge.jtds.jdbc.JtdsConnection.(JtdsConnection.java:359)
at net.sourceforge.jtds.jdbc.Driver.connect(Driver.java:184)
at java.sql.DriverManager.getConnection(DriverManager.java:179)
at java.sql.DriverManager.getConnection(DriverManager.java:144)
at com.example.test.MainActivity.connectionclass(MainActivity.java:158)
at com.example.test.MainActivity$CheckLogin.doInBackground(MainActivity.java:109)
at com.example.test.MainActivity$CheckLogin.doInBackground(MainActivity.java:76)
at android.os.AsyncTask$2.call(AsyncTask.java:288)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) 
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 
at java.lang.Thread.run(Thread.java:841) 
I/Process: Sending signal. PID: 22838 SIG: 9
Application terminated.

any advice to correct my problem thanks in advance..