how to update sqlite db in Android?

I want to update one row based on multiple row value, After run the application getting error like = ( FATAL EXCEPTION: main android.database.sqlite.SQLiteException: near "=": syntax error (code 1): , while compiling: UPDATE Tablename SET sFollowed=?,Code=?,Name=? WHERE Vessel_Name= )

Here is my update method in MyDbhelper class

public boolean update_isFollowed(String strVesselName , String strVesselNotationNumber, String strIsFollowed) {
        SQLiteDatabase db1 = getReadableDatabase();

        ContentValues values=new ContentValues();
        values.put(COL_VesselName,strVesselName );
        values.put(COL_ClassCodeNumber , strVesselNotationNumber);
        values.put(COL_IsFollowedVessels, strIsFollowed);

       int id=db1.update(Table_VesselList,values,COL_ClassCodeNumber + "=" +strVesselNotationNumber +" and "+ COL_VesselName +"="+strVesselName,null);

        return id > 0;
    }