问java.sql。网络适配器无法建立连接？

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(Unknown Source)

at java.sql.DriverManager.getConnection(Unknown Source)

at com.gg.tools.DBHelper.getConnection(DBHelper.java:49)

at com.gg.dao.AccountDao.insert(AccountDao.java:25)

at Test.main(Test.java:15)

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)

... 9 more

Caused by: java.net.ConnectException: Connection timed out: connect

at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)

at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)

at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)

at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)

at java.net.AbstractPlainSocketImpl.connect(Unknown Source)

at java.net.PlainSocketImpl.connect(Unknown Source)

at java.net.SocksSocketImpl.connect(Unknown Source)

at java.net.Socket.connect(Unknown Source)

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)

... 14 more

Exception in thread "main" java.lang.NullPointerException

at com.gg.dao.AccountDao.insert(AccountDao.java:26)

at Test.main(Test.java:15)