Java連接池和線程池是Java編程中非常重要的概念，它們在提高程序的性能和并發能力方面起到了重要作用。

Java連接池是一組連接的集合，以便在需要時可以重復使用這些連接。連接池靠近到數據庫，允許程序直接從連接池中獲取數據庫連接，減少因為頻繁建立連接而帶來的性能開銷。

下面是一個簡單的Java連接池的代碼示例：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
public class ConnectionPool {
private static ConnectionPool instance = null;
private List<Connection> connectionList = new ArrayList<Connection>();
private String url = "jdbc:mysql://localhost:3306/mydatabase";
private String username = "root";
private String password = "password";
private ConnectionPool() {
try {
Class.forName("com.mysql.jdbc.Driver");
for (int i = 0; i < 10; i++) {
Connection connection = DriverManager.getConnection(url, username, password);
connectionList.add(connection);
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static ConnectionPool getInstance() {
if (instance == null) {
synchronized (ConnectionPool.class) {
if (instance == null) {
instance = new ConnectionPool();
}
}
}
return instance;
}
public synchronized Connection getConnection() {
if (connectionList.isEmpty()) {
return null;
}
Connection connection = connectionList.get(0);
connectionList.remove(0);
return connection;
}
public synchronized void releaseConnection(Connection connection) {
connectionList.add(connection);
}
}

Java線程池是用來管理多個線程的線程隊列。它能夠幫助控制線程數，節省資源，提高性能。多個任務可以由一個線程池管理，避免在大量任務到來時產生線程的創建和銷毀的開銷。

下面是一個簡單的Java線程池的代碼示例：

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class ThreadPoolExample {
public static void main(String[] args) {
ExecutorService executorService = Executors.newFixedThreadPool(4);
for (int i = 0; i < 10; i++) {
executorService.execute(new Runnable() {
public void run() {
System.out.println(Thread.currentThread().getName() + " is working");
}
});
}
executorService.shutdown();
}
}

總結來說，Java連接池和線程池在Java編程中起到了重要作用，對于提高程序性能和并發能力有著非常重要的幫助。