我的線程程序不起作用，因為我希望它起作用。首先是我的主類，從那里開始我的線程：import static java.lang.Thread.currentThread;public class Main {public static void main(String[] args) throws IOException, NamingException, ClassNotFoundException {    Properties property = new Properties();    property.load(new FileReader(new File(args[0])));    DataSource ds = DataSource.newInstance(property);    Class.forName("org.postgresql.Driver");    ConnectionPool connectionPool = new ConnectionPool();    System.out.println(currentThread().getName());    ConnectionPoolManager manager = new ConnectionPoolManager(connectionPool, ds);    manager.start();    }}這是我的 ConnectionPool 類package com.telbook.connectionPooling;import java.sql.Connection;import java.sql.SQLException;import java.util.ArrayList;import java.util.List;public class ConnectionPool {private List<PoolObject> poolObjects = new ArrayList<>();public List<PoolObject> getPoolObjects() {    return poolObjects;}public void setPoolObjects(List<PoolObject> poolObjects) {    this.poolObjects = poolObjects;}public void put(Connection connection) {    PoolObject poolObject = new PoolObject();    poolObject.setConnection(connection);    poolObjects.add(poolObject);}public Connection getConnection() throws SQLException {    for (PoolObject object: poolObjects) {        if (!object.getInUse() && object.getConnection()!=null) {            if (!object.getConnection().isClosed()) {                if (object.getConnection().isValid(50)) {                    object.setInUse(true);                    return object.getConnection();                }            }        }    }    return null;}}