URL (Java SE 21 & JDK 21)
Description: declaration: module: java.base, package: java.net, class: URL
Keywords: java.net.URL class

Module java.base
Package java.net

# Class URL

java.lang.Object
java.net.URL

All Implemented Interfaces:
  `Serializable`

public final class URL extends Object implements Serializable
Class `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: Types of URL

In general, a URL can be broken into several parts. Consider the following example:

>          http://www.example.com/docs/resource1.html

The URL above indicates that the protocol to use is `http` (HyperText Transfer Protocol) and that the information resides on a host machine named `www.example.com`. The information on that host machine is named `/docs/resource1.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 path component.

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.example.com:1080/docs/resource1.html

The syntax of `URL` is defined by RFC 2396: Uniform Resource Identifiers (URI): Generic Syntax, amended by RFC 2732: Format for Literal IPv6 Addresses in URLs. The Literal IPv6 address format also supports scope_ids. The syntax and usage of scope_ids is described here.

A URL may have appended to it a "fragment", also known as a "ref" or a "reference". The fragment is indicated by the sharp sign character "#" followed by more characters. For example,

>          http://www.example.com/index.html#chapter1

This fragment 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://www.example.com/index.html

contained within it the relative URL:

>          FAQ.html

it would be a shorthand for:

>          http://www.example.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 fragment is not inherited.

## Constructing instances of `URL`

The `java.net.URL` constructors are deprecated. Developers are encouraged to use `java.net.URI` to parse or construct a `URL`. In cases where an instance of `java.net.URL` is needed to open a connection, `URI` can be used to construct or parse the URL string, possibly calling `URI.parseServerAuthority()` to validate that the authority component can be parsed as a server-based authority, and then calling `URI.toURL()` to create the `URL` instance.

The URL constructors are specified to throw `MalformedURLException` but the actual parsing/validation that is performed is implementation dependent. Some parsing/validation may be delayed until later, when the underlying stream handler's implementation is called. Being able to construct an instance of `URL` doesn't provide any guarantee about its conformance to the URL syntax specification.

The URL class does not itself encode or decode any URL components according to the escaping mechanism defined in RFC2396. It is the responsibility of the caller to encode any fields, which need to be escaped prior to calling URL, and also to decode any escaped fields, that are returned from URL. Furthermore, because URL has no knowledge of URL escaping, it does not recognise equivalence between the encoded or decoded form of the same URL. For example, the two URLs:

        http://foo.com/hello world/ and http://foo.com/hello%20world

would be considered not equal to each other.

Note, the `URI` class does perform escaping of its component fields in certain circumstances. The recommended way to manage the encoding and decoding of URLs is to use `URI`, and to convert between these two classes using `toURI()` and `URI.toURL()`.

The `URLEncoder` and `URLDecoder` classes can also be used, but only for HTML form encoding, which is not the same as the encoding scheme defined in RFC2396.

API Note:
  Applications working with file paths and file URIs should take great care to use the appropriate methods to convert between the two. The `Path.of(URI)` factory method and the `File(URI)` constructor can be used to create `Path` or `File` objects from a file URI. `Path.toUri()` and `File.toURI()` can be used to create a `URI` from a file path, which can be converted to URL using `URI.toURL()`. Applications should never try to construct or parse a `URL` from the direct string representation of a `File` or `Path` instance.

  Before constructing a `URL` from a `URI`, and depending on the protocol involved, applications should consider validating whether the URI authority can be parsed as server-based.

  Some components of a URL or URI, such as userinfo, may be abused to construct misleading URLs or URIs. Applications that deal with URLs or URIs should take into account the recommendations advised in RFC3986, Section 7, Security Considerations.

  All `URL` constructors may throw `MalformedURLException`. In particular, if the underlying `URLStreamHandler` implementation rejects, or is known to reject, any of the parameters, `MalformedURLException` may be thrown. Typically, a constructor that calls the stream handler's parseURL method may throw `MalformedURLException` if the underlying stream handler implementation of that method throws `IllegalArgumentException`. However, which checks are performed, or not, by the stream handlers is implementation dependent, and callers should not rely on such checks for full URL validation.

Since:
  1.0
External Specifications
  - RFC 2396: Uniform Resource Identifiers (URI): Generic Syntax
  - RFC 2732: Format for Literal IPv6 Addresses in URL's
  - RFC 3986: Uniform Resource Identifier (URI): Generic Syntax
See Also:
  - Serialized Form

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `URL(String spec)`
  Deprecated.
  Use `URI.toURL()` to construct an instance of URL.
  `URL(String protocol, String host, int port, String file)`
  Deprecated.
  Use `URI.toURL()` to construct an instance of URL.
  `URL(String protocol, String host, int port, String file, URLStreamHandler handler)`
  Deprecated.
  Use `of(URI, URLStreamHandler)` to construct an instance of URL associated with a custom protocol handler.
  `URL(String protocol, String host, String file)`
  Deprecated.
  Use `URI.toURL()` to construct an instance of URL.
  `URL(URL context, String spec)`
  Deprecated.
  Use `URI.toURL()` to construct an instance of URL.
  `URL(URL context, String spec, URLStreamHandler handler)`
  Deprecated.
  Use `of(URI, URLStreamHandler)` to construct an instance of URL associated with a custom protocol handler.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `equals(Object obj)`
  Compares this URL for equality with another object.
  `String`
  `getAuthority()`
  Gets the authority part of this `URL`.
  `final Object`
  `getContent()`
  Gets the contents of this URL.
  `final Object`
  `getContent(Class<?>[] classes)`
  Gets the contents of this URL.
  `int`
  `getDefaultPort()`
  Gets the default port number of the protocol associated with this `URL`.
  `String`
  `getFile()`
  Gets the file name of this `URL`.
  `String`
  `getHost()`
  Gets the host name of this `URL`, if applicable.
  `String`
  `getPath()`
  Gets the path part of this `URL`.
  `int`
  `getPort()`
  Gets the port number of this `URL`.
  `String`
  `getProtocol()`
  Gets the protocol name of this `URL`.
  `String`
  `getQuery()`
  Gets the query part of this `URL`.
  `String`
  `getRef()`
  Gets the anchor (also known as the "reference") of this `URL`.
  `String`
  `getUserInfo()`
  Gets the userInfo part of this `URL`.
  `int`
  `hashCode()`
  Creates an integer suitable for hash table indexing.
  `static URL`
  `of(URI uri, URLStreamHandler handler)`
  Creates a URL from a URI, as if by invoking `uri.toURL()`, but associating it with the given `URLStreamHandler`, if allowed.
  `URLConnection`
  `openConnection()`
  Returns a `URLConnection` instance that represents a connection to the remote object referred to by the `URL`.
  `URLConnection`
  `openConnection(Proxy proxy)`
  Same as `openConnection()`, except that the connection will be made through the specified proxy; Protocol handlers that do not support proxying will ignore the proxy parameter and make a normal connection.
  `final InputStream`
  `openStream()`
  Opens a connection to this `URL` and returns an `InputStream` for reading from that connection.
  `boolean`
  `sameFile(URL other)`
  Compares two URLs, excluding the fragment component.
  `static void`
  `setURLStreamHandlerFactory(URLStreamHandlerFactory fac)`
  Sets an application's `URLStreamHandlerFactory`.
  `String`
  `toExternalForm()`
  Constructs a string representation of this `URL`.
  `String`
  `toString()`
  Constructs a string representation of this `URL`.
  `URI`
  `toURI()`
  Returns a `URI` equivalent to this URL.

  ### Methods declared in class java.lang.Object

  `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- ## Constructor Details

  - ### URL

    @Deprecated(since="20") public URL(String protocol, String host, int port, String file) throws MalformedURLException
    Deprecated.
    Use `URI.toURL()` to construct an instance of URL. See the note on constructor deprecation for more details.
    Creates a `URL` object from the specified `protocol`, `host`, `port` number, and `file`.

    `host` can be expressed as a host name or a literal IP address. If IPv6 literal address is used, it should be enclosed in square brackets (`'['` and `']'`), as specified by RFC 2732; However, the literal IPv6 address format defined in RFC 2373: IP Version 6 Addressing Architecture is also accepted.

    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:

    1. If the application has previously set up an instance of `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.
    2. If no `URLStreamHandlerFactory` has yet been set up, or if the factory's `createURLStreamHandler` method returns `null`, then the ServiceLoader mechanism is used to locate URLStreamHandlerProvider implementations using the system class loader. The order that providers are located is implementation specific, and an implementation is free to cache the located providers. A ServiceConfigurationError, `Error` or `RuntimeException` thrown from the `createURLStreamHandler`, if encountered, will be propagated to the calling thread. The `createURLStreamHandler` method of each provider, if instantiated, is invoked, with the protocol string, until a provider returns non-null, or all providers have been exhausted.
    3. If the previous step fails to find a protocol handler, the constructor reads the value of the system property:

       > `java.protocol.handler.pkgs`

       If the value of that system property is not `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`

       where `<package>` is replaced by the name of the package and `<protocol>` is replaced by the name of the protocol. If this class does not exist, or if the class exists but it is not a subclass of `URLStreamHandler`, then the next package in the list is tried.
    4. If the previous step fails to find a protocol handler, then the constructor tries to load a built-in protocol handler. If this class does not exist, or if the class exists but it is not a subclass of `URLStreamHandler`, then a `MalformedURLException` is thrown.

    Protocol handlers for the following protocols are guaranteed to exist on the search path:

    - `http`
    - `https`
    - `file`
    - `jar`
    Protocol handlers for additional protocols may also be available. Some protocol handlers, for example those used for loading platform classes or classes on the class path, may not be overridden. The details of such restrictions, and when those restrictions apply (during initialization of the runtime for example), are implementation specific and therefore not specified

    No validation of the inputs is performed by this constructor.

    Parameters:
      `protocol` - the name of the protocol to use.
      `host` - the name of the host.
      `port` - the port number on the host.
      `file` - the file on the host
    Throws:
      `MalformedURLException` - if an unknown protocol or the port is a negative number other than -1, or if the underlying stream handler implementation rejects, or is known to reject, the `URL`
    External Specifications
      - RFC 2373: IP Version 6 Addressing Architecture
      - RFC 2732: Format for Literal IPv6 Addresses in URL's
    See Also:
      - `System.getProperty(java.lang.String)`
      - `setURLStreamHandlerFactory(java.net.URLStreamHandlerFactory)`
      - `URLStreamHandler`
      - `URLStreamHandlerFactory.createURLStreamHandler(java.lang.String)`

  - ### URL

    @Deprecated(since="20") public URL(String protocol, String host, String file) throws MalformedURLException
    Deprecated.
    Use `URI.toURL()` to construct an instance of URL. See the note on constructor deprecation for more details.
    Creates a URL from the specified `protocol` name, `host` name, and `file` name. The default port for the specified protocol is used.

    This constructor is equivalent to the four-argument constructor with the only difference of using the default port for the specified protocol. No validation of the inputs is performed by this constructor.

    Parameters:
      `protocol` - the name of the protocol to use.
      `host` - the name of the host.
      `file` - the file on the host.
    Throws:
      `MalformedURLException` - if an unknown protocol is specified, or if the underlying stream handler implementation rejects, or is known to reject, the `URL`
    See Also:
      - `URL(java.lang.String, java.lang.String, int, java.lang.String)`

  - ### URL

    @Deprecated(since="20") public URL(String protocol, String host, int port, String file, URLStreamHandler handler) throws MalformedURLException
    Deprecated.
    Use `of(URI, URLStreamHandler)` to construct an instance of URL associated with a custom protocol handler. See the note on constructor deprecation for more details.
    Creates a `URL` object from the specified `protocol`, `host`, `port` number, `file`, and `handler`. Specifying a `port` number of `-1` indicates that the URL should use the default port for the protocol. Specifying a `handler` of `null` indicates that the URL should use a default stream handler for the protocol, as outlined for: `URL(java.lang.String, java.lang.String, int, java.lang.String)`

    If the handler is not null and there is a security manager, the security manager's `checkPermission` method is called with a `NetPermission("specifyStreamHandler")` permission. This may result in a SecurityException. No validation of the inputs is performed by this constructor.

    Parameters:
      `protocol` - the name of the protocol to use.
      `host` - the name of the host.
      `port` - the port number on the host.
      `file` - the file on the host
      `handler` - the stream handler for the URL.
    Throws:
      `MalformedURLException` - if an unknown protocol or the port is a negative number other than -1, or if the underlying stream handler implementation rejects, or is known to reject, the `URL`
      `SecurityException` - if a security manager exists and its `checkPermission` method doesn't allow specifying a stream handler explicitly.
    See Also:
      - `System.getProperty(java.lang.String)`
      - `setURLStreamHandlerFactory(java.net.URLStreamHandlerFactory)`
      - `URLStreamHandler`
      - `URLStreamHandlerFactory.createURLStreamHandler(java.lang.String)`
      - `SecurityManager.checkPermission(java.security.Permission)`
      - `NetPermission`

  - ### URL

    @Deprecated(since="20") public URL(String spec) throws MalformedURLException
    Deprecated.
    Use `URI.toURL()` to construct an instance of URL. See the note on constructor deprecation for more details.
    Creates a `URL` object from the `String` representation.

    This constructor is equivalent to a call to the two-argument constructor with a `null` first argument.

    Parameters:
      `spec` - the `String` to parse as a URL.
    Throws:
      `MalformedURLException` - if no protocol is specified, or an unknown protocol is found, or `spec` is `null`, or the parsed URL fails to comply with the specific syntax of the associated protocol, or the underlying stream handler's parseURL method throws `IllegalArgumentException`
    See Also:
      - `URL(java.net.URL, java.lang.String)`

  - ### URL

    @Deprecated(since="20") public URL(URL context, String spec) throws MalformedURLException
    Deprecated.
    Use `URI.toURL()` to construct an instance of URL. See the note on constructor deprecation for more details.
    Creates a URL by parsing the given spec within a specified context. The new URL is created from the given context URL and the spec argument as described in RFC2396 "Uniform Resource Identifiers : Generic Syntax" :

    >               <scheme>://<authority><path>?<query>#<fragment>

    The reference is parsed into the scheme, authority, path, query and fragment parts. If the path component is empty and the scheme, authority, and query components are undefined, then the new URL is a reference to the current document. Otherwise, the fragment and query parts present in the spec are used in the new URL.

    If the scheme component is defined in the given spec and does not match the scheme of the context, then the new URL is created as an absolute URL based on the spec alone. Otherwise the scheme component is inherited from the context URL.

    If the authority component is present in the spec then the spec is treated as absolute and the spec authority and path will replace the context authority and path. If the authority component is absent in the spec then the authority of the new URL will be inherited from the context.

    If the spec's path component begins with a slash character "/" then the path is treated as absolute and the spec path replaces the context path.

    Otherwise, the path is treated as a relative path and is appended to the context path, as described in RFC2396. Also, in this case, the path is canonicalized through the removal of directory changes made by occurrences of ".." and ".".

    For a more detailed description of URL parsing, refer to RFC2396.

    Implementation Requirements:
      Parsing the URL includes calling the `parseURL` method on the selected handler.
    Parameters:
      `context` - the context in which to parse the specification.
      `spec` - the `String` to parse as a URL.
    Throws:
      `MalformedURLException` - if no protocol is specified, or an unknown protocol is found, or `spec` is `null`, or the parsed URL fails to comply with the specific syntax of the associated protocol, or the underlying stream handler's parseURL method throws `IllegalArgumentException`
    See Also:
      - `URL(java.lang.String, java.lang.String, int, java.lang.String)`
      - `URLStreamHandler`
      - `URLStreamHandler.parseURL(java.net.URL, java.lang.String, int, int)`

  - ### URL

    @Deprecated(since="20") public URL(URL context, String spec, URLStreamHandler handler) throws MalformedURLException
    Deprecated.
    Use `of(URI, URLStreamHandler)` to construct an instance of URL associated with a custom protocol handler. See the note on constructor deprecation for more details.
    Creates a URL by parsing the given spec with the specified handler within a specified context. If the handler is null, the parsing occurs as with the two argument constructor.
    Implementation Requirements:
      Parsing the URL includes calling the `parseURL` method on the selected handler.
    Parameters:
      `context` - the context in which to parse the specification.
      `spec` - the `String` to parse as a URL.
      `handler` - the stream handler for the URL.
    Throws:
      `MalformedURLException` - if no protocol is specified, or an unknown protocol is found, or `spec` is `null`, or the parsed URL fails to comply with the specific syntax of the associated protocol, or the underlying stream handler's parseURL method throws `IllegalArgumentException`
      `SecurityException` - if a security manager exists and its `checkPermission` method doesn't allow specifying a stream handler.
    See Also:
      - `URL(java.lang.String, java.lang.String, int, java.lang.String)`
      - `URLStreamHandler`
      - `URLStreamHandler.parseURL(java.net.URL, java.lang.String, int, int)`

- ## Method Details

  - ### of

    public static URL of(URI uri, URLStreamHandler handler) throws MalformedURLException
    Creates a URL from a URI, as if by invoking `uri.toURL()`, but associating it with the given `URLStreamHandler`, if allowed.
    API Note:
      Applications should consider performing additional integrity checks before constructing a `URL` and opening a connection. See the API note in the class level API documentation.
    Implementation Requirements:
      The implementation of this method includes calling the `parseURL` method on the selected handler.
    Parameters:
      `uri` - the `URI` from which the returned `URL` should be built
      `handler` - a custom protocol stream handler for the returned `URL`. Can be `null`, in which case the default stream handler for the protocol if any, will be used.
    Returns:
      a new `URL` instance created from the given `URI` and associated with the given `URLStreamHandler`, if any
    Throws:
      `NullPointerException` - if `uri` is `null`
      `IllegalArgumentException` - if no protocol is specified (the uri scheme is `null`), or if the `URLStreamHandler` is not `null` and can not be set for the given protocol
      `MalformedURLException` - if an unknown protocol is found, or the given URI fails to comply with the specific syntax of the associated protocol, or the underlying stream handler's parseURL method throws `IllegalArgumentException`
      `SecurityException` - if a security manager exists and its `checkPermission` method doesn't allow specifying a stream handler
    Since:
      20
    See Also:
      - `URI.toURL()`

  - ### getQuery

    public String getQuery()
    Gets the query part of this `URL`.
    Returns:
      the query part of this `URL`, or `null` if one does not exist
    Since:
      1.3

  - ### getPath

    public String getPath()
    Gets the path part of this `URL`.
    Returns:
      the path part of this `URL`, or an empty string if one does not exist
    Since:
      1.3

  - ### getUserInfo

    public String getUserInfo()
    Gets the userInfo part of this `URL`.
    Returns:
      the userInfo part of this `URL`, or `null` if one does not exist
    Since:
      1.3

  - ### getAuthority

    public String getAuthority()
    Gets the authority part of this `URL`.
    Returns:
      the authority part of this `URL`
    Since:
      1.3

  - ### getPort

    public int getPort()
    Gets the port number of this `URL`.
    Returns:
      the port number, or -1 if the port is not set

  - ### getDefaultPort

    public int getDefaultPort()
    Gets the default port number of the protocol associated with this `URL`. If the URL scheme or the URLStreamHandler for the URL do not define a default port number, then -1 is returned.
    Returns:
      the port number
    Since:
      1.4

  - ### getProtocol

    public String getProtocol()
    Gets the protocol name of this `URL`.
    Returns:
      the protocol of this `URL`.

  - ### getHost

    public String getHost()
    Gets the host name of this `URL`, if applicable. The format of the host conforms to RFC 2732, i.e. for a literal IPv6 address, this method will return the IPv6 address enclosed in square brackets (`'['` and `']'`).
    Returns:
      the host name of this `URL`.

  - ### getFile

    public String getFile()
    Gets the file name of this `URL`. The returned file portion will be the same as `getPath()`, plus the concatenation of the value of `getQuery()`, if any. If there is no query portion, this method and `getPath()` will return identical results.
    Returns:
      the file name of this `URL`, or an empty string if one does not exist

  - ### getRef

    public String getRef()
    Gets the anchor (also known as the "reference") of this `URL`.
    Returns:
      the anchor (also known as the "reference") of this `URL`, or `null` if one does not exist

  - ### equals

    public boolean equals(Object obj)
    Compares this URL for equality with another object.

    If the given object is not a URL then this method immediately returns `false`.

    Two URL objects are equal if they have the same protocol, reference equivalent hosts, have the same port number on the host, and the same file and fragment of the file.

    Two hosts are considered equivalent if both host names can be resolved into the same IP addresses; else if either host name can't be resolved, the host names must be equal without regard to case; or both host names equal to null.

    Since hosts comparison requires name resolution, this operation is a blocking operation.

    Note: The defined behavior for `equals` is known to be inconsistent with virtual hosting in HTTP.

    Overrides:
      `equals` in class `Object`
    Parameters:
      `obj` - the URL to compare against.
    Returns:
      `true` if the objects are the same; `false` otherwise.
    See Also:
      - `Object.hashCode()`
      - `HashMap`

  - ### hashCode

    public int hashCode()
    Creates an integer suitable for hash table indexing.

    The hash code is based upon all the URL components relevant for URL comparison. As such, this operation is a blocking operation.

    Overrides:
      `hashCode` in class `Object`
    Returns:
      a hash code for this `URL`.
    See Also:
      - `Object.equals(java.lang.Object)`
      - `System.identityHashCode(java.lang.Object)`

  - ### sameFile

    public boolean sameFile(URL other)
    Compares two URLs, excluding the fragment component.

    Returns `true` if this `URL` and the `other` argument are equal without taking the fragment component into consideration.

    Parameters:
      `other` - the `URL` to compare against.
    Returns:
      `true` if they reference the same remote object; `false` otherwise.

  - ### toString

    public String toString()
    Constructs a string representation of this `URL`. The string is created by calling the `toExternalForm` method of the stream protocol handler for this object.
    Overrides:
      `toString` in class `Object`
    Returns:
      a string representation of this object.
    See Also:
      - `URL(java.lang.String, java.lang.String, int, java.lang.String)`
      - `URLStreamHandler.toExternalForm(java.net.URL)`

  - ### toExternalForm

    public String toExternalForm()
    Constructs a string representation of this `URL`. The string is created by calling the `toExternalForm` method of the stream protocol handler for this object.
    Returns:
      a string representation of this object.
    See Also:
      - `URL(java.lang.String, java.lang.String, int, java.lang.String)`
      - `URLStreamHandler.toExternalForm(java.net.URL)`

  - ### toURI

    public URI toURI() throws URISyntaxException
    Returns a `URI` equivalent to this URL. This method functions in the same way as `new URI (this.toString())`.

    Note, any URL instance that complies with RFC 2396 can be converted to a URI. However, some URLs that are not strictly in compliance can not be converted to a URI.

    Returns:
      a URI instance equivalent to this URL.
    Throws:
      `URISyntaxException` - if this URL is not formatted strictly according to RFC2396 and cannot be converted to a URI.
    Since:
      1.5

  - ### openConnection

    public URLConnection openConnection() throws IOException
    Returns a `URLConnection` instance that represents a connection to the remote object referred to by the `URL`.

    A new instance of URLConnection is created every time when invoking the URLStreamHandler.openConnection(URL) method of the protocol handler for this URL.

    It should be noted that a URLConnection instance does not establish the actual network connection on creation. This will happen only when calling URLConnection.connect().

    If for the URL's protocol (such as HTTP or JAR), there exists a public, specialized URLConnection subclass belonging to one of the following packages or one of their subpackages: java.lang, java.io, java.util, java.net, the connection returned will be of that subclass. For example, for HTTP an HttpURLConnection will be returned, and for JAR a JarURLConnection will be returned.

    Returns:
      a `URLConnection` linking to the URL.
    Throws:
      `IOException` - if an I/O exception occurs.
    See Also:
      - `URL(java.lang.String, java.lang.String, int, java.lang.String)`

  - ### openConnection

    public URLConnection openConnection(Proxy proxy) throws IOException
    Same as `openConnection()`, except that the connection will be made through the specified proxy; Protocol handlers that do not support proxying will ignore the proxy parameter and make a normal connection. Invoking this method preempts the system's default `ProxySelector` settings.
    Parameters:
      `proxy` - the Proxy through which this connection will be made. If direct connection is desired, Proxy.NO_PROXY should be specified.
    Returns:
      a `URLConnection` to the URL.
    Throws:
      `IOException` - if an I/O exception occurs.
      `SecurityException` - if a security manager is present and the caller doesn't have permission to connect to the proxy.
      `IllegalArgumentException` - will be thrown if proxy is null, or proxy has the wrong type
      `UnsupportedOperationException` - if the subclass that implements the protocol handler doesn't support this method.
    Since:
      1.5
    See Also:
      - `URL(java.lang.String, java.lang.String, int, java.lang.String)`
      - `URLConnection`
      - `URLStreamHandler.openConnection(java.net.URL, java.net.Proxy)`

  - ### openStream

    public final InputStream openStream() throws IOException
    Opens a connection to this `URL` and returns an `InputStream` for reading from that connection. This method is a shorthand for:

    >          openConnection().getInputStream()

    Returns:
      an input stream for reading from the URL connection.
    Throws:
      `IOException` - if an I/O exception occurs.
    See Also:
      - `openConnection()`
      - `URLConnection.getInputStream()`

  - ### getContent

    public final Object getContent() throws IOException
    Gets the contents of this URL. This method is a shorthand for:

    >          openConnection().getContent()

    Returns:
      the contents of this URL.
    Throws:
      `IOException` - if an I/O exception occurs.
    See Also:
      - `URLConnection.getContent()`

  - ### getContent

    public final Object getContent(Class<?>[] classes) throws IOException
    Gets the contents of this URL. This method is a shorthand for:

    >          openConnection().getContent(classes)

    Parameters:
      `classes` - an array of Java types
    Returns:
      the content object of this URL that is the first match of the types specified in the classes array. null if none of the requested types are supported.
    Throws:
      `IOException` - if an I/O exception occurs.
    Since:
      1.3
    See Also:
      - `URLConnection.getContent(Class[])`

  - ### setURLStreamHandlerFactory

    public static void setURLStreamHandlerFactory(URLStreamHandlerFactory fac)
    Sets an application's `URLStreamHandlerFactory`. This method can be called at most once in a given Java Virtual Machine.

    The `URLStreamHandlerFactory` instance is used to construct a stream protocol handler from a protocol name.

    If there is a security manager, this method first calls the security manager's `checkSetFactory` method to ensure the operation is allowed. This could result in a SecurityException.

    Parameters:
      `fac` - the desired factory.
    Throws:
      `Error` - if the application has already set a factory.
      `SecurityException` - if a security manager exists and its `checkSetFactory` method doesn't allow the operation.
    See Also:
      - `URL(java.lang.String, java.lang.String, int, java.lang.String)`
      - `URLStreamHandlerFactory`
      - `SecurityManager.checkSetFactory()`