java写数据库连接_JAVA写简单的数据库连接池

好的，我可以帮您解答。下面是一个简单的Java数据库连接池的示例代码：

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 final String DB_DRIVER = "com.mysql.cj.jdbc.Driver";
    private static final String DB_URL = "jdbc:mysql://localhost:3306/mydatabase";
    private static final String DB_USERNAME = "root";
    private static final String DB_PASSWORD = "password";
    
    private static final int MAX_CONNECTIONS = 10;
    
    private List<Connection> connectionPool;
    private List<Connection> usedConnections = new ArrayList<>();
    
    private static ConnectionPool instance = new ConnectionPool();
    
    private ConnectionPool() {
        connectionPool = new ArrayList<>();
        try {
            Class.forName(DB_DRIVER);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    
    private Connection createConnection() throws SQLException {
        Connection connection = DriverManager.getConnection(DB_URL, DB_USERNAME, DB_PASSWORD);
        return connection;
    }
    
    public static ConnectionPool getInstance() {
        return instance;
    }
    
    public synchronized Connection getConnection() throws SQLException {
        if (connectionPool.isEmpty()) {
            return createConnection();
        } else {
            Connection connection = connectionPool.remove(connectionPool.size() - 1);
            usedConnections.add(connection);
            return connection;
        }
    }
    
    public synchronized void releaseConnection(Connection connection) {
        connectionPool.add(connection);
        usedConnections.remove(connection);
    }
    
    public int getSize() {
        return connectionPool.size() + usedConnections.size();
    }
    
    public void closeAllConnections() throws SQLException {
        for (Connection connection : connectionPool) {
            connection.close();
        }
        for (Connection connection : usedConnections) {
            connection.close();
        }
        connectionPool.clear();
        usedConnections.clear();
    }
}

该示例代码中，我们使用了Java的线程安全的List来保存空闲连接和已使用连接。在创建连接时，我们使用了Java的JDBC API来获取数据库连接。在获取连接时，我们首先检查连接池中是否有空闲连接。如果没有，则创建新连接。如果有，则从连接池中获取一个连接。在释放连接时，我们将其添加回连接池中。

希望这个示例代码能够帮助您理解如何编写一个简单的Java数据库连接池。