java连接数据库怎么实现增删改查功能

1、导入必要的包：

```java

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

```

2、建立数据库连接：

```java

String url = "jdbc:mysql://localhost:3306/mydatabase";

String username = "root";

String password = "password";

Connection conn = DriverManager.getConnection(url, username, password);

```

3、实现查询功能：

```java

String query = "SELECT * FROM mytable";

PreparedStatement statement = conn.prepareStatement(query);

ResultSet result = statement.executeQuery();

while (result.next()) {

// 处理结果集

}

```

4、实现插入功能：

```java

String insertQuery = "INSERT INTO mytable (column1, column2) VALUES (?, ?)";

PreparedStatement insertStatement = conn.prepareStatement(insertQuery);

insertStatement.setString(1, "value1");

insertStatement.setString(2, "value2");

insertStatement.executeUpdate();

```

5、实现更新功能：

```java

String updateQuery = "UPDATE mytable SET column1 = ? WHERE column2 = ?";

PreparedStatement updateStatement = conn.prepareStatement(updateQuery);

updateStatement.setString(1, "new value");

updateStatement.setString(2, "target value");

updateStatement.executeUpdate();

```

6、实现删除功能：

```java

String deleteQuery = "DELETE FROM mytable WHERE column = ?";

PreparedStatement deleteStatement = conn.prepareStatement(deleteQuery);

deleteStatement.setString(1, "target value");

deleteStatement.executeUpdate();

```

以上是一个简单的示例，实际情况中可能需要根据具体需求进行更复杂的操作。同时，为了保证代码的健壮性和安全性，通常需要添加异常处理、连接管理等功能。