Class.forName()与newInstance()

 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.ResultSet;
 import java.sql.Statement;
 import java.util.Date;

 public class NewInstanceExample {

     public static void main(String[] args) throws Exception {
         //Class.forName()要求JVM查找并加载指定的类
         //newInstance()获取类的实例
         //newInstance()方法和new关键字区别：一个是方法，一个是关键字,newInstance()只能调用无参的构造函数
         //forName和newInstance获得更好的灵活性，提供了一种降耦的手段
         Date date = java.util.Date.class.newInstance();
         long time = date.getTime();
         System.out.println(time);

         Class<?> dateClass = Class.forName("java.util.Date");
         Date date2 = (Date) dateClass.newInstance();
         long time2 = date2.getTime();
         System.out.println(time2);

         mysqlConnection();

     }

     public static void mysqlConnection() throws Exception {
         //在JDBC规范中明确要求Driver类必须向DriverManager注册自己
         //类似如下：
         /*
         public class MyJDBCDriver implements Driver {
             static {
                 DriverManager.registerDriver(new MyJDBCDriver());
             }
         }
         */
         //Class.forName()在加载com.mysql.jdbc.Driver时，会执行静态代码块，向DriverManager注册自己
         Class.forName("com.mysql.jdbc.Driver");
         String url = "jdbc:mysql://localhost/test?useUnicode=true&&characterEncoding=UTF-8&autoReconnect=true";
         String user = "root";
         String password = "123456";

         Connection conn = null;
         Statement stmt = null;
         ResultSet rs = null;
         try {
             conn = DriverManager.getConnection(url, user, password);
             stmt = conn.createStatement();
             String sql = "select deptno,deptname from dept";// dept这张表有deptno，deptname字段
             rs = stmt.executeQuery(sql);// 执行sql语句
             while (rs.next()) {
                 System.out.print(rs.getInt("deptno") + "    ");
                 System.out.println(rs.getString("deptname"));
             }
         } catch (Exception e) {
             throw e;
         } finally {
             rs.close();
             stmt.close();
             conn.close();
         }
     }
 }