连接数据库查询数据时出现异常java.sql.SQLException: Io 异常: The Network Adapter could not establ

请各位高手看看为什么 package jdbc_example.i3102;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class JDBCModel {
    public static void main(String[] args) {
        try {
            Class.forName("oracle.jdbc.OracleDriver");
            Connection con = DriverManager.getConnection(
                    "jdbc:oracle:thin:@localhost:1521:PBDEMO", "DBDEMO",
                    "SA");

            Statement stmt = con.createStatement();
            ResultSet rs = stmt.executeQuery("SELECT * FROM us");
            System.out.println("姓名\t性别\t");
            while (rs.next()) {
                String name = rs.getString("username");
                int gender = rs.getInt("易做图");

                System.out.println(name+"\t"+gender+"\t");
            }
            con.close();
        } catch (ClassNotFoundException e) {
            System.out.println("无法找到驱动类");
        }catch (SQLException e) {
            e.printStackTrace();
        }

    }
}

java.sql.SQLException: Io 异常: The Network Adapter could not establish the connection
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:112)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:146)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:255)
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:387)
at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:414)
at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:165)
at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:35)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:801)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at jdbc_example.i3102.JDBCModel.main(JDBCModel.java:13) --------------------编程问答-------------------- Class.forName("oracle.jdbc.OracleDriver").newInstance;

在检查一下数据库有没启动，用sqlplus连接一下看看。如果sqlplus连接不上就是数据库问题咯。 --------------------编程问答-------------------- oracle.jdbc.OracleDriver改成oracle.jdbc.driver.OracleDriver --------------------编程问答-------------------- Class.forName("oracle.jdbc.driver.OracleDriver"); --------------------编程问答-------------------- 检查数据库驱动

补充：Java ,  Eclipse