try
        {
              Class.forName("oracle.jdbc.driver.OracleDriver");
              Connection con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl", "scott", "tiger");
              if (con == null)
                  System.out.println("Connection not successful");
              else
                  System.out.print("successful....");
              con.close();
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }

Error:

java.sql.SQLException: The Network Adapter could not establish the connection
	at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:412)
	at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:531)
	at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:221)
	at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32)
	at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:503)
	at java.sql.DriverManager.getConnection(DriverManager.java:579)
	at java.sql.DriverManager.getConnection(DriverManager.java:221)
	at Orajdbc.main(Orajdbc.java:20)
Caused by: oracle.net.ns.NetException: The Network Adapter could not establish the connection
	at oracle.net.nt.ConnStrategy.execute(ConnStrategy.java:359)
	at oracle.net.resolver.AddrResolution.resolveAndExecute(AddrResolution.java:422)
	at oracle.net.ns.NSProtocol.establishConnection(NSProtocol.java:672)
	at oracle.net.ns.NSProtocol.connect(NSProtocol.java:237)
	at oracle.jdbc.driver.T4CConnection.connect(T4CConnection.java:1042)
	at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:301)
	... 7 more
Caused by: java.net.ConnectException: Connection refused: connect
	at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
	at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:75)
	at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:337)
	at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:198)
	at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:180)
	at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:157)
	at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:391)
	at java.net.Socket.connect(Socket.java:579)
	at oracle.net.nt.TcpNTAdapter.connect(TcpNTAdapter.java:141)
	at oracle.net.nt.ConnOption.connect(ConnOption.java:123)
	at oracle.net.nt.ConnStrategy.execute(ConnStrategy.java:337)
	... 12 more

I am using windows vista 32 bit Business version
Jdk 1.6
Oracle Driver "ojdbc6.jar" set in classpath enviroument variable
Oracle 11.2.0.1

Is the database really running on the port 1521 of your machine? Are you able to connect to that SID using SQL Developer?

Sohanlal: you are facing what problem?
start a new thread and post the exact error YOU get in there. don't continue this thread, since it's a dead thread that shouldn't have been revived.