public abstract class SocketFactory {private static SocketFactory theFactory;　　//返回环境默认的socket工厂的副本。public static SocketFactory getDefault() {synchronized (SocketFactory.class) {if (theFactory == null) {theFactory = new DefaultSocketFactory();}}return theFactory;}　　//创建一个无连接的socket(抛出SocketException("Unconnected sockets not implemented")异常)public Socket createSocket() throws IOException {UnsupportedOperationException localUnsupportedOperationException = new UnsupportedOperationException();SocketException localSocketException = new SocketException("Unconnected sockets not implemented");localSocketException.initCause(localUnsupportedOperationException);throw localSocketException;}//创建一个套接字并将其连接到指定地址的指定端口号。public abstract Socket createSocket(String host, int port) throws IOException, UnknownHostException;　//创建套接字并将其连接到指定远程主机的指定远程端口号。public abstract Socket createSocket(String host, int port, InetAddress localHost, int localPort)throws IOException, UnknownHostException;//创建一个套接字并将其连接到指定地址的指定端口号。public abstract Socket createSocket(InetAddress address, int port) throws IOException;//创建套接字并将其连接到指定远程地址上的指定远程端口。public abstract Socket createSocket(InetAddress address, int port, InetAddress localAdress,int localPort) throws IOException;
}

class DefaultSocketFactory extends SocketFactory {public Socket createSocket() {return new Socket();}public Socket createSocket(String paramString, int paramInt) throws IOException, UnknownHostException {return new Socket(paramString, paramInt);}public Socket createSocket(InetAddress paramInetAddress, int paramInt) throws IOException {return new Socket(paramInetAddress, paramInt);}public Socket createSocket(String paramString, int paramInt1, InetAddress paramInetAddress, int paramInt2)throws IOException, UnknownHostException {return new Socket(paramString, paramInt1, paramInetAddress, paramInt2);}public Socket createSocket(InetAddress paramInetAddress1, int paramInt1, InetAddress paramInetAddress2,int paramInt2) throws IOException {return new Socket(paramInetAddress1, paramInt1, paramInetAddress2, paramInt2);}
}

public abstract class ServerSocketFactory {private static ServerSocketFactory theFactory;//返回环境默认的socket工厂副本
    public static ServerSocketFactory getDefault() {synchronized (ServerSocketFactory.class) {if (theFactory == null) {theFactory = new DefaultServerSocketFactory();}}return theFactory;}//返回一个未绑定的服务器套间字
    public ServerSocket createServerSocket() throws IOException {throw new SocketException("Unbound server sockets not implemented");}//返回一个绑定到指定端口的服务器套间字
    public abstract ServerSocket createServerSocket(int port) throws IOException;//返回一个绑定到指定端口的服务器套间字，并指定backlog参数
    public abstract ServerSocket createServerSocket(int port, int backlog) throws IOException;//返回一个绑定到指定端口的服务间套间字，并指定backlog和ip地址
    public abstract ServerSocket createServerSocket(int port, int backlog, InetAddress adress)throws IOException;
}                

class DefaultServerSocketFactory extends ServerSocketFactory {public ServerSocket createServerSocket() throws IOException {return new ServerSocket();}public ServerSocket createServerSocket(int paramInt) throws IOException {return new ServerSocket(paramInt);}public ServerSocket createServerSocket(int paramInt1, int paramInt2) throws IOException {return new ServerSocket(paramInt1, paramInt2);}public ServerSocket createServerSocket(int paramInt1, int paramInt2, InetAddress paramInetAddress)throws IOException {return new ServerSocket(paramInt1, paramInt2, paramInetAddress);}
}

class TestFactory extends SocketFactory {@Overridepublic Socket createSocket(String paramString, int paramInt) throws IOException, UnknownHostException {return null;}@Overridepublic Socket createSocket(String paramString, int paramInt1, InetAddress paramInetAddress, int paramInt2)throws IOException, UnknownHostException {return null;}@Overridepublic Socket createSocket(InetAddress paramInetAddress, int paramInt) throws IOException {return null;}@Overridepublic Socket createSocket(InetAddress paramInetAddress1, int paramInt1, InetAddress paramInetAddress2,int paramInt2) throws IOException {return null;}public static void main(String[] args) throws UnknownHostException, IOException {TestFactory factory = new TestFactory();Socket socket1 = factory.createSocket("host", 1);System.out.println(socket1 == null);SocketFactory factory1 =  SocketFactory.getDefault();Socket socket2 = factory.createSocket("host", 1);System.out.println(socket2 == null);}
}