jdbc连接，操作

package jdbca;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Statement;
import com.mysql.jdbc.Driver;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import com.mysql.jdbc.Driver;

public class DemoPreparedstement {
public static void testselect(int cno) throws Exception {
DriverManager.registerDriver(new Driver());
// Class.forName("com.mysql.jdbc.Driver");
// 2.获取连接对象
String url = "jdbc:mysql://localhost:3306/a";
Connection conn = DriverManager.getConnection(url, "root", "cjx990725");
// 3.获取载体
PreparedStatement pstmt = conn.prepareStatement("select * from coure where cno=?");
// 给？设置值,从左到右赋值,序号从1开始,
pstmt.setInt(1, cno);
// 执行
ResultSet rs = pstmt.executeQuery();//执行操作
if (rs.next()) {
int id = rs.getInt(1);
String name = rs.getString(2);
int cpno = rs.getInt(3);
int ss = rs.getInt(4);
System.out.println(id + " " + name + " " + cpno + " " + ss);
}

}

public static void update(int cno,String cname) throws SQLException{
DriverManager.registerDriver(new Driver());
String url="jdbc:mysql://localhost:3306/a";
Connection conn=DriverManager.getConnection(url, "root", "cjx990725");
System.out.println(conn);
PreparedStatement pstmt = conn.prepareStatement("update coure set cname=? where cno=?");
pstmt.setString(1, cname);
pstmt.setInt(2, cno);
int n= pstmt.executeUpdate();//返回int类型
System.out.println(n);
pstmt.close();
conn.close();
}
public static void delete(int cno) throws SQLException{
DriverManager.registerDriver(new Driver());
String url="jdbc:mysql://localhost:3306/a";
Connection conn=DriverManager.getConnection(url, "root", "cjx990725");
System.out.println(conn);
PreparedStatement pstmt = conn.prepareStatement("delete from coure where cno=?");
pstmt.setInt(1, cno);
int n= pstmt.executeUpdate();
System.out.println(n);
pstmt.close();
conn.close();
}
public static void insert(String cname,int cpno,int ccredit,int cno) throws SQLException{
DriverManager.registerDriver(new Driver());
String url="jdbc:mysql://localhost:3306/a";
Connection conn=DriverManager.getConnection(url, "root", "cjx990725");
PreparedStatement pstmt = conn.prepareStatement("insert into coure(cno,cname,cpno,ccredit) values(?,?,?,?)");
pstmt.setString(2, cname);
pstmt.setInt(3, cpno);
pstmt.setInt(4, ccredit);
pstmt.setInt(1, cno);
int n= pstmt.executeUpdate();
System.out.println(n);
pstmt.close();
conn.close();
}
public static void main(String[] args) throws Exception {
//testselect(5);
//insert("李四",5,6,9);
update(9,"张三");
//delete(9);
}
}