ExecutorService executor = Executors.newFixedThreadPool(20);
   DBConnectDev dbConnectdb=null;

    try{
    List<Runnable> tasks = new ArrayList<>();


        xxtList.forEach(xxDVO -> {

        Runnable runnable = new Runnable() {
            public void run() {

                ThreadProcess.controlProcess(dbConnectdb,xxDVO,Thread.currentThread().getId());
            }
        };
        tasks.add(runnable);
    });

    CompletableFuture<?>[] futures = tasks.stream().map(task -> CompletableFuture.runAsync(task, executor))
            .toArray(CompletableFuture[]::new);
    CompletableFuture.allOf(futures).join();

    if(Globals.THREAD_COUNT>0){
        Globals.THREAD_COUNT=Globals.THREAD_COUNT-1;

    }
    executor.shutdown();
    executor.awaitTermination(3, TimeUnit.SECONDS);

} catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
    dbConnectdb.closeAllConnection();

}

public static void spasKontrolIslem(DBConnectDev dbConnectionManager){


    Connection connection=null;

    try {

       connection = dbConnectionManager.getConnectionFromPool();
      //database processes

    } catch (Exception e) {

        e.printStackTrace();
    }
    finally {
        if (connection != null)
               dbConnectionManager.returnConnectionToPool(connection);
 }



}

public class DBConnectDev {String driver = "com.ibm.db2.jcc.DB2Driver";

final int MAX_POOL_SIZE = 20;
Vector<Connection> connectionPool = new Vector<>();

public DBConnectDev() {
    initialize();
}

private void initialize() {
    for (int i = 0; i < MAX_POOL_SIZE; i++)
        initializeConnectionPool();
}

private void initializeConnectionPool() {
    while (!checkIfConnectionPoolIsFull()) {
        connectionPool.addElement(createNewConnectionForPool());
    }
}

private synchronized boolean checkIfConnectionPoolIsFull() {
    if (connectionPool.size() < MAX_POOL_SIZE)
        return false;
    return true;
}

private Connection createNewConnectionForPool() {
    Connection connection=null;

        try {
            Context ctx=new InitialContext();
            DataSource  ds  = (DataSource)
     ctx.lookup("JNDINAME");

            connection=(Connection) ds.getConnection();

        } catch (NamingException e) {   e.printStackTrace();    } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    return connection;
}

public synchronized Connection getConnectionFromPool() {
    Connection connection = null;

    if (connectionPool.size() > 0) {
        connection = (Connection) connectionPool.firstElement();
        connectionPool.removeElementAt(0);
    }
    return connection;
}

public synchronized void returnConnectionToPool(Connection connection) {
    connectionPool.addElement(connection);
}

public void closeAllConnection(){

    if (connectionPool.size() > 0) {
        connectionPool.forEach(connection -> {
            try {
                ((Connection)connection).close();
            } catch (SQLException e) {
                System.out.println("dev Connection kapatmada hata oluştu");
            }
        });
        connectionPool.removeAllElements();
    }
}