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java.lang.Object | +----java.net.URL
URL represents a Uniform Resource Locator, a pointer to a "resource" on the World Wide Web. A resource can be something as simple as a file or a directory, or it can be a reference to a more complicated object, such as a query to a database or to a search engine. More information on the types of URLs and their formats can be found at: http://www.ncsa.uiuc.edu/demoweb/url-primer.html In general, a URL can be broken into several parts. The previous example of a URL indicates that the protocol to use is http (HyperText Transport Protocol) and that the information resides on a host machine named www.ncsa.uiuc.edu. The information on that host machine is named demoweb/url-primer.html. The exact meaning of this name on the host machine is both protocol dependent and host dependent. The information normally resides in a file, but it could be generated on the fly. This component of the URL is called the file component, even though the information is not necessarily in a file.
A URL can optionally specify a "port", which is the port number to which the TCP connection is made on the remote host machine. If the port is not specified, the default port for the protocol is used instead. For example, the default port for http is 80. An alternative port could be specified as:
http://www.ncsa.uiuc.edu:8080/demoweb/url-primer.html A URL may have appended to it an "anchor", also known as a "ref" or a "reference". The anchor is indicated by the sharp sign character "#" followed by more characters. For example,
http://java.sun.com/index.html#chapter1 This anchor is not technically part of the URL. Rather, it indicates that after the specified resource is retrieved, the application is specifically interested in that part of the document that has the tag chapter1 attached to it. The meaning of a tag is resource specific.
An application can also specify a "relative URL", which contains only enough information to reach the resource relative to another URL. Relative URLs are frequently used within HTML pages. For example, if the contents of the URL:
http://java.sun.com/index.html FAQ.html http://java.sun.com/FAQ.html The relative URL need not specify all the components of a URL. If the protocol, host name, or port number is missing, the value is inherited from the fully specified URL. The file component must be specified. The optional anchor is not inherited.
URL(String) URL object from the String representation. URL(String, String, int, String) URL object from the specified protocol, host, port number, and file. URL(String, String, String) protocol name, host name, and file name. URL(URL, String) spec within a specified context. 
equals(Object) getContent() getFile() URL. getHost() URL, if applicable. getPort() URL. getProtocol() URL. getRef() URL. hashCode() openConnection() URLConnection object that represents a connection to the remote object referred to by the URL. openStream() URL and returns an InputStream for reading from that connection. sameFile(URL) set(String, String, int, String, String) 
setURLStreamHandlerFactory(URLStreamHandlerFactory) URLStreamHandlerFactory. toExternalForm() URL. toString() URL. 
URL
public URL(String protocol,
String host,
int port,
String file) throws MalformedURLException
URL object from the specified protocol, host, port number, and file. Specifying a port number of -1 indicates that the URL should use the default port for the protocol. If this is the first URL object being created with the specified protocol, a stream protocol handler object, an instance of class URLStreamHandler, is created for that protocol:
URLStreamHandlerFactory as the stream handler factory, then the createURLStreamHandler method of that instance is called with the protocol string as an argument to create the stream protocol handler. URLStreamHandlerFactory has yet been set up, or if the factory's createURLStreamHandler method returns null, then the constructor finds the value of the system property: java.handler.protol.pkgs null, it is interpreted as a list of packages separated by a vertical slash character '|'. The constructor tries to load the class named: <package>.<protocol>.Handler URLStreamHandler, then the next package in the list is tried. sun.net.www.protocol.<protocol>.Handler URLStreamHandler, then a MalformedURLException is thrown. URL
public URL(String protocol, String host, String file) throws MalformedURLException
protocol name, host name, and file name. The default port for the specified protocol is used. This method is equivalent to calling the four-argument constructor with the arguments being protocol, host, -1, and file.
URL
public URL(String spec) throws MalformedURLException
URL object from the String representation. This constructor is equivalent to a call to the two-argument constructor with a null first argument.
String to parse as a URL. URL
public URL(URL context, String spec) throws MalformedURLException
spec within a specified context. If the context argument is not null and the spec argument is a partial URL specification, then any of the strings missing components are inherited from the context argument. The specification given by the String argument is parsed to determine if it specifies a protocol. If the String contains an ASCII colon ':' character before the first occurrence of an ASCII slash character '/', then the characters before the colon comprise the protocol.
spec argument does not specify a protocol: null, then the protocol is copied from the context argument. null, then a MalformedURLException is thrown. spec argument does specify a protocol: null, or specifies a different protocol than the specification argument, the context argument is ignored. null and specifies the same protocol as the specification, the host, port number, and file are copied from the context argument into the newly created URL. The constructor then searches for an appropriate stream protocol handler of type URLStreamHandler as outlined for:
java.net.URL#URL(java.lang.String, java.lang.String, int, java.lang.String) parseURL method is called to parse the remaining fields of the specification that override any defaults set by the context argument. String representation of a URL. 
set
protected void set(String protocol,
String host,
int port,
String file,
String ref)
getPort
public int getPort()
URL. Returns -1 if the port is not set. getProtocol
public String getProtocol()
URL. URL. getHost
public String getHost()
URL, if applicable. For "file" protocol, this is an empty string. URL. getFile
public String getFile()
URL. URL. getRef
public String getRef()
URL. URL. equals
public boolean equals(Object obj)
true if and only if the argument is not null and is a URL object that represents the same URL as this object. Two URL objects are equal if they have the same protocol and reference the same host, the same port number on the host, and the same file on the host. The anchors of the URL objects are not compared. This method is equivalent to:
(obj instanceof URL) && sameFile((URL)obj) true if the objects are the same; false otherwise. hashCode
public int hashCode()
URL. sameFile
public boolean sameFile(URL other)
true if this URL and the other argument both refer to the same resource. The two URLs might not both contain the same anchor. URL to compare against. true if they reference the same remote object; false otherwise. toString
public String toString()
URL. The string is created by calling the toExternalForm method of the stream protocol handler for this object. toExternalForm
public String toExternalForm()
URL. The string is created by calling the toExternalForm method of the stream protocol handler for this object. openConnection
public URLConnection openConnection() throws IOException
URLConnection object that represents a connection to the remote object referred to by the URL. If there is not already an open connection, the connection is opened by calling the openConnection method of the protocol handler for this URL.
URLConnection to the URL. openStream
public final InputStream openStream() throws IOException
URL and returns an InputStream for reading from that connection. This method is a shorthand for: openConnection().getInputStream() getContent
public final Object getContent() throws IOException
openConnection().getContent() 
setURLStreamHandlerFactory
public static synchronized void setURLStreamHandlerFactory(URLStreamHandlerFactory fac)
URLStreamHandlerFactory. This method can be called at most once by an application. The URLStreamHandlerFactory instance is used to construct a stream protocol handler from a protocol name.
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