1。可以用在url中的字符

  • The capital letters A-Z

  • The lowercase letters a-z

  • The digits 0-9

  • The punctuation characters - _ . ! ~ * ' (and ,)

2。URLEncoder.encode(,)方法：把空格变成＋，其他非字符的符号用%和十六进制数表示。
URLDecoder.decode(,)方法与之对应，一般第二个参数用"UTF-8"

3。URI＝URL＋URN

  • The URI class is purely about identification of resources and parsing of URIs. It provides no methods to retrieve a representation of the resource identified by its URI.

  • The URI class is more conformant to the relevant specifications than the URL class.

  • A URI object can represent a relative URI. The URL class absolutizes all URIs before storing them.

URI格式scheme:scheme-specific-part:fragment

URI的几个方法，构造函数，relative函数，relativize函数。


4。代理的几个方法
a System Properties
b Proxy类
    SocketAddress address = new InetSocketAddress("proxy.example.com", 80);
    Proxy proxy = new Proxy(Proxy.Type.HTTP, address);

  • Proxy.Type.DIRECT

  • Proxy.Type.HTTP

  • Proxy.Type.SOCKS

c ProxySelector 类
   集成这个类并实现 public abstract List<Proxy> select(URI uri) 
public void connectFailed(URI uri, SocketAddress address, IOException ex)
这两个方法。
  

5。