OS: Ubuntu
Java Version:  1.5.0_16-b02
               1.6.0_17-b04
Database: Oracle 11g Release 11.1.0.6.0

> Connecting to oracle
    java.sql.SQLException: Io exception: Connection reset
    at oracle.jdbc.driver.SQLStateMapping.newSQLException(SQLStateMapping.java:74)
    at oracle.jdbc.driver.DatabaseError.newSQLException(DatabaseError.java:110)
    at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:171)
    at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:227)
    at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:494)
    at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:411)
    at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:490)
    at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:202)
    at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:33)
    at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:474)
    at java.sql.DriverManager.getConnection(DriverManager.java:525)
    at java.sql.DriverManager.getConnection(DriverManager.java:171)
    at TestConnect.main(TestConnect.java:13)

import java.io.*;
import java.sql.*;
public class TestConnect {
    public static void main(String[] args) {
        try {
            System.out.println("Connecting to oracle");
            Connection con=null;
            Class.forName("oracle.jdbc.driver.OracleDriver");
            con=DriverManager.getConnection(
               "jdbc:oracle:thin:@172.16.48.100:1535:sample",
               "JOHN",
               "90009000");
            System.out.println("Connected to oracle");
            con.close();
            System.out.println("Goodbye");
        } catch(Exception e) { e.printStackTrace(); }
    }
}

"main" prio=10 tid=0x00007f7cc8009000 nid=0x2f3a runnable [0x00007f7cce69e000]
   java.lang.Thread.State: RUNNABLE
        at java.net.Inet4AddressImpl.getLocalHostName(Native Method)
        at java.net.InetAddress.getLocalHost(InetAddress.java:1444)
        at sun.security.provider.SeedGenerator$1.run(SeedGenerator.java:176)
        at sun.security.provider.SeedGenerator$1.run(SeedGenerator.java:162)
        at java.security.AccessController.doPrivileged(Native Method)

$ hostname
my.server.com

127.0.0.1 my my.server.com

SQL> SELECT PASSWORD_VERSIONS FROM DBA_USERS WHERE USERNAME='SCOTT';

PASSWORD_VERSIONS
-----------------
11G 12C

SQL> alter user scott identified by "tiger";

User altered.

SQL> SELECT PASSWORD_VERSIONS FROM DBA_USERS WHERE USERNAME='SCOTT';
PASSWORD_VERSIONS
-----------------
10G 11G 12C

run -> services.msc