Oracle JDBC problem

Question

When I compile this code:
package DataBase;
// Import Java package for File I/O
import java.io.*;
import java.sql.*;
import java.util.*;
import javax.naming.NamingException;
import javax.sql.*;
import oracle.jdbc.driver.*;
import oracle.jdbc.pool.*;
/*** <p>Title: </p>** <p>Description: </p>** <p>Copyright: Copyright (c) 2004</p>** <p>Company: </p>** @author not attributable* @version 1.0*/
class access_database {
public access_database() {
try {jbInit();}
catch (Exception ex) {ex.printStackTrace();}}
public static void main (String[] args) throws SQLException, IOException{
//Load and register Oracle driver
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
//Establish a connection
Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@127.0.0.1:1521:ORCL", "scott", "tiger");
//Create a Statement object
Statement sql_stmt = conn.createStatement();
//Create a ResultSet object, execute the query and return a// resultset
ResultSet rset = sql_stmt.executeQuery("SELECT empno, ename, sal, deptno FROM emp ORDER BY ename");
//Process the resultset, retrieve data in each row, column by column//and write to an operating system file
String str = "";
while (rset.next()){str += rset.getInt(1)+" "+ rset.getString(2)+" "+rset.getFloat(3)+" "+rset.getInt(4)+"\n";}
byte buf[] = str.getBytes();
OutputStream fp = new FileOutputStream("c:\\query1.lst");
fp.write(buf);
fp.close();
//Close the ResultSet and Statement
rset.close();
sql_stmt.close();
//Close the database connection
conn.close();}
private void jbInit() throws Exception {}}
I get errors:
Exception in thread main
java.sql.SQLException: Io exception: The Network Adapter could not establish the connection
     at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:134)
     at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:179)
     at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:333)
     at oracle.jdbc.driver.OracleConnection.<init>(OracleConnection.java:404)
     at oracle.jdbc.driver.OracleDriver.getConnectionInstance(OracleDriver.java:468)
     at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:314)
     at java.sql.DriverManager.getConnection(DriverManager.java:512)
     at java.sql.DriverManager.getConnection(DriverManager.java:171)
     at DataBase.access_database.main(DataBase.java:19)
Process exited with exit code
And a windows appear:
Fatal exception occur. Program will exit.
How can I repair this code to run perfectly?

Answer 1

The Network Adapter exception is caused because:
1.     The database host name or port number is wrong.
2.     The database TNSListener has not been started. The TNSListener may be started with the lsnrctl utility.
C:\>lsnrctl start