java 找不到指定类时发生的异常（ClassNotFoundException）

package Chapter04.check; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement; public class CheckException_01 { public static void main(String[] args) throws Exception { Connection conn = null; Statement stmt = null; ResultSet rst = null; String s = ""; Class.forName("com.mysql.jdbc.Driver"); // 注册驱动程序 conn = DriverManager.getConnection( "jdbc:mysql://localhost:3306/myuser", "root", "root"); // 获得数据库的连接 stmt = conn.createStatement(); // 创建会话声明 rst = stmt.executeQuery("select * from user"); while (rst.next()) { System.out.print(s = new String(rst.getString(1).getBytes( "ISO-8859-1"), "GBK") + "--"); System.out.print(s = new String(rst.getString(2).getBytes( "ISO-8859-1"), "GBK") + "--"); System.out.print(s = new String(rst.getString(3).getBytes( "ISO-8859-1"), "GBK") + "--"); System.out.print(s = new String(rst.getString(4).getBytes( "ISO-8859-1"), "GBK")); System.out.println(); } } }