Below is a simple example of java method which will return true if given database contains any table by name DB_VERSION. Else it returns false.

 /*
     * isRegistryDBConfigured()    method returns true if provided Database
     * contains table DB_VERSION. Returns false if it doesn't contain
     * that table.
     */
    public boolean isRegistryDBConfigured(String dbName, String portNumber,String userName, String password) {
        try {
          String hostName = InetAddress.getLocalHost().getCanonicalHostName();
            Class.forName("com.ibm.db2.jcc.DB2Driver");
            StringBuffer dbConnectionURL = new StringBuffer("jdbc:db2://");
            dbConnectionURL.append(hostName + ":" + portNumber + "/" + dbName);
            Connection db2Conn = DriverManager.getConnection(
                    dbConnectionURL.toString(), userName, password);
//Connection db2Conn = DriverManager.getConnection("jdbc:db2j:net://localhost:50000/frsdb","db2admin","db2admin");          
 // Connection db2Conn =  DriverManager.getConnection("jdbc:db2://localhost:50000/test","db2admin","db2admin");
            Statement st = db2Conn.createStatement();
            String myQuery = "SELECT TABNAME FROM SYSCAT.TABLES WHERE TABNAME ='DB_VERSION'";
            ResultSet resultSet = st.executeQuery(myQuery);
            while (resultSet.next()) {
                String name = resultSet.getString("TABNAME");
                if (name.equals("DB_VERSION")) {
                    System.out.println("Tablename:" + name);
                    return true;
                }
            }
            resultSet.close();
            st.close();
            db2Conn.close();
           
        } catch (Exception e) {
            System.out.println("EXCEPTION::" + e);
        }
        return false;
    }