Adds a general request property specified by a key-value pair.

  Adds a general request property specified by a
key-value pair. This method will not overwrite
existing values associated with the same key.
Parameters:
- key - the keyword by which the request is known (e.g., "accept").
- value - the value associated with it.
Throws:
- IllegalStateException - if already connected
- NullPointerException - if key is null
Since: 1.4
See Also: URLConnection.getRequestProperties(),

  Opens a communications link to the resource referenced by this URL, if such a connection has not already been established.

  Opens a communications link to the resource referenced by this URL, if such a connection has not already been established.

If the connect method is called when the connection has already been opened (indicated by the connected field having the value true), the call is ignored.

URLConnection objects go through two phases: first they are created, then they are connected. After being created, and before being connected, various options can be specified (e.g., doInput and UseCaches). After connecting, it is an error to try to set them. Operations that depend on being connected, like getContentLength, will implicitly perform the connection, if necessary.
Throws:
- SocketTimeoutException - if the timeout expires before the connection can be established
- IOException - if an I/O error occurs while opening the connection.
See Also: URLConnection.connected, URLConnection.getConnectTimeout(), URLConnection.setConnectTimeout(int),

  Returns the value of the allowUserInteraction field for this object.

  Returns the value of the allowUserInteraction field for
this object.
Returns: the value of the allowUserInteraction field for this object.
See Also: URLConnection.setAllowUserInteraction(boolean),

  Returns setting for connect timeout.

  Returns setting for connect timeout.

0 return implies that the option is disabled (i.e., timeout of infinity).
Returns: an int that indicates the connect timeout value in milliseconds
Since: 1.5
See Also: URLConnection.setConnectTimeout(int), URLConnection.connect(),

  Retrieves the contents of this URL connection.

  Retrieves the contents of this URL connection.

This method first determines the content type of the object by calling the getContentType method. If this is the first time that the application has seen that specific content type, a content handler for that content type is created:

1. If the application has set up a content handler factory instance using the setContentHandlerFactory method, the createContentHandler method of that instance is called with the content type as an argument; the result is a content handler for that content type.
2. If no content handler factory has yet been set up, or if the factory's createContentHandler method returns null, then the application loads the class named:

            sun.net.www.content.<contentType>
        

   where <contentType> is formed by taking the content-type string, replacing all slash characters with a period ('.'), and all other non-alphanumeric characters with the underscore character '_'. The alphanumeric characters are specifically the 26 uppercase ASCII letters 'A' through 'Z', the 26 lowercase ASCII letters 'a' through 'z', and the 10 ASCII digits '0' through '9'. If the specified class does not exist, or is not a subclass of ContentHandler, then an UnknownServiceException is thrown.

Returns: the object fetched. The instanceof operator should be used to determine the specific kind of object returned.
Throws:
- IOException - if an I/O error occurs while getting the content.
- UnknownServiceException - if the protocol does not support the content type.
See Also: ContentHandlerFactory.createContentHandler(java.lang.String), URLConnection.getContentType(), URLConnection.setContentHandlerFactory(java.net.ContentHandlerFactory),

  Retrieves the contents of this URL connection.

  Retrieves the contents of this URL connection.
Returns: the object fetched that is the first match of the type specified in the classes array. null if none of the requested types are supported. The instanceof operator should be used to determine the specific kind of object returned.
Parameters:
- classes - the Class array indicating the requested types
Throws:
- IOException - if an I/O error occurs while getting the content.
- UnknownServiceException - if the protocol does not support the content type.
Since: 1.3
See Also: URLConnection.getContent(), ContentHandlerFactory.createContentHandler(java.lang.String), URLConnection.getContent(java.lang.Class[]), URLConnection.setContentHandlerFactory(java.net.ContentHandlerFactory),

  Returns the value of the content-encoding header field.

  Returns the value of the content-encoding header field.
Returns: the content encoding of the resource that the URL references, or null if not known.
See Also: URLConnection.getHeaderField(java.lang.String),

  Gets the Content Handler appropriate for this connection.

  Gets the Content Handler appropriate for this connection.
Parameters:
- connection - the connection to use.

  Returns the value of the content-length header field.

  Returns the value of the content-length header field.
Returns: the content length of the resource that this connection's URL references, or -1 if the content length is not known.

  Returns the value of the content-type header field.

  Returns the value of the content-type header field.
Returns: the content type of the resource that the URL references, or null if not known.
See Also: URLConnection.getHeaderField(java.lang.String),

  Returns the value of the date header field.

  Returns the value of the date header field.
Returns: the sending date of the resource that the URL references, or 0 if not known. The value returned is the number of milliseconds since January 1, 1970 GMT.
See Also: URLConnection.getHeaderField(java.lang.String),

  Returns the default value of the allowUserInteraction field.

  Returns the default value of the allowUserInteraction field.

Ths default is "sticky", being a part of the static state of all URLConnections. This flag applies to the next, and all following URLConnections that are created.
Returns: the default value of the allowUserInteraction field.
See Also: URLConnection.setDefaultAllowUserInteraction(boolean),

  Returns the value of the default request property.

  Returns the value of the default request property. Default request
properties are set for every connection.
Returns: the value of the default request property for the specified key.
Parameters:
- key - the keyword by which the request is known (e.g., "accept").
See Also: URLConnection.getRequestProperty(java.lang.String), URLConnection.setDefaultRequestProperty(java.lang.String, java.lang.String),

  Returns the default value of a URLConnection's useCaches flag.

  Returns the default value of a URLConnection's useCaches flag.

Ths default is "sticky", being a part of the static state of all URLConnections. This flag applies to the next, and all following URLConnections that are created.
Returns: the default value of a URLConnection's useCaches flag.
See Also: URLConnection.setDefaultUseCaches(boolean),

  Returns the value of this URLConnection's doInput flag.

  Returns the value of this URLConnection's
doInput flag.
Returns: the value of this URLConnection's doInput flag.
See Also: URLConnection.setDoInput(boolean),

  Returns the value of this URLConnection's doOutput flag.

  Returns the value of this URLConnection's
doOutput flag.
Returns: the value of this URLConnection's doOutput flag.
See Also: URLConnection.setDoOutput(boolean),

  Returns the value of the expires header field.

  Returns the value of the expires header field.
Returns: the expiration date of the resource that this URL references, or 0 if not known. The value is the number of milliseconds since January 1, 1970 GMT.
See Also: URLConnection.getHeaderField(java.lang.String),

  Loads filename map (a mimetable) from a data file.

  Loads filename map (a mimetable) from a data file. It will
first try to load the user-specific table, defined
by "content.types.user.table" property. If that fails,
it tries to load the default built-in table at
lib/content-types.properties under java home.
Returns: the FileNameMap
Since: 1.2
See Also: URLConnection.setFileNameMap(java.net.FileNameMap),

  Returns the value for the n^th header field.

  Returns the value for the n^th header field. It returns null if there are fewer than n+1fields.

This method can be used in conjunction with the getHeaderFieldKey method to iterate through all the headers in the message.
Returns: the value of the n^th header field or null if there are fewer than n+1 fields
Parameters:
- n - an index, where n>=0
See Also: URLConnection.getHeaderFieldKey(int),

  Returns the value of the named header field.

  Returns the value of the named header field.

If called on a connection that sets the same header multiple times with possibly different values, only the last value is returned.
Returns: the value of the named header field, or null if there is no such field in the header.
Parameters:
- name - the name of a header field.

  Returns the value of the named field parsed as date.

  Returns the value of the named field parsed as date. The result is the number of milliseconds since January 1, 1970 GMT represented by the named field.

This form of getHeaderField exists because some connection types (e.g., http-ng) have pre-parsed headers. Classes for that connection type can override this method and short-circuit the parsing.
Returns: the value of the field, parsed as a date. The value of the Default argument is returned if the field is missing or malformed.
Parameters:
- name - the name of the header field.
- Default - a default value.

  Returns the value of the named field parsed as a number.

  Returns the value of the named field parsed as a number.

This form of getHeaderField exists because some connection types (e.g., http-ng) have pre-parsed headers. Classes for that connection type can override this method and short-circuit the parsing.
Returns: the value of the named field, parsed as an integer. The Default value is returned if the field is missing or malformed.
Parameters:
- name - the name of the header field.
- Default - the default value.

  Returns the key for the n^th header field.

  Returns the key for the n^th header field.
It returns null if there are fewer than n+1 fields.
Returns: the key for the n^th header field, or null if there are fewer than n+1 fields.
Parameters:
- n - an index, where n>=0

  Returns an unmodifiable Map of the header fields.

  Returns an unmodifiable Map of the header fields.
The Map keys are Strings that represent the
response-header field names. Each Map value is an
unmodifiable List of Strings that represents
the corresponding field values.
Returns: a Map of header fields
Since: 1.4

  Returns the value of this object's ifModifiedSince field.

  Returns the value of this object's ifModifiedSince field.
Returns: the value of this object's ifModifiedSince field.
See Also: URLConnection.setIfModifiedSince(long),

  Returns an input stream that reads from this open connection.

  Returns an input stream that reads from this open connection.

A SocketTimeoutException can be thrown when reading from the
returned input stream if the read timeout expires before data
is available for read.
Returns: an input stream that reads from this open connection.
Throws:
- IOException - if an I/O error occurs while creating the input stream.
- UnknownServiceException - if the protocol does not support input.
See Also: URLConnection.setReadTimeout(int), URLConnection.getReadTimeout(),

  Returns the value of the last-modified header field.

  Returns the value of the last-modified header field.
The result is the number of milliseconds since January 1, 1970 GMT.
Returns: the date the resource referenced by this URLConnection was last modified, or 0 if not known.
See Also: URLConnection.getHeaderField(java.lang.String),

  Returns an output stream that writes to this connection.

  Returns an output stream that writes to this connection.
Returns: an output stream that writes to this connection.
Throws:
- IOException - if an I/O error occurs while creating the output stream.
- UnknownServiceException - if the protocol does not support output.

  Returns a permission object representing the permission necessary to make the connection represented by this object.

  Returns a permission object representing the permission necessary to make the connection represented by this object. This method returns null if no permission is required to make the connection. By default, this method returns java.security.AllPermission. Subclasses should override this method and return the permission that best represents the permission required to make a a connection to the URL. For example, a URLConnection representing a file: URL would return a java.io.FilePermission object.

The permission returned may dependent upon the state of the connection. For example, the permission before connecting may be different from that after connecting. For example, an HTTP sever, say foo.com, may redirect the connection to a different host, say bar.com. Before connecting the permission returned by the connection will represent the permission needed to connect to foo.com, while the permission returned after connecting will be to bar.com.

Permissions are generally used for two purposes: to protect caches of objects obtained through URLConnections, and to check the right of a recipient to learn about a particular URL. In the first case, the permission should be obtained after the object has been obtained. For example, in an HTTP connection, this will represent the permission to connect to the host from which the data was ultimately fetched. In the second case, the permission should be obtained and tested before connecting.
Returns: the permission object representing the permission necessary to make the connection represented by this URLConnection.
Throws:
- IOException - if the computation of the permission requires network or file I/O and an exception occurs while computing it.

  Returns setting for read timeout.

  Returns setting for read timeout. 0 return implies that the
option is disabled (i.e., timeout of infinity).
Returns: an int that indicates the read timeout value in milliseconds
Since: 1.5
See Also: URLConnection.setReadTimeout(int), InputStream.read(),

  Returns an unmodifiable Map of general request properties for this connection.

  Returns an unmodifiable Map of general request
properties for this connection. The Map keys
are Strings that represent the request-header
field names. Each Map value is a unmodifiable List
of Strings that represents the corresponding
field values.
Returns: a Map of the general request properties for this connection.
Throws:
- IllegalStateException - if already connected
Since: 1.4

  Returns the value of the named general request property for this connection.

  Returns the value of the named general request property for this
connection.
Returns: the value of the named general request property for this connection. If key is null, then null is returned.
Parameters:
- key - the keyword by which the request is known (e.g., "accept").
Throws:
- IllegalStateException - if already connected
See Also: URLConnection.setRequestProperty(java.lang.String, java.lang.String),

  Returns the value of this URLConnection's URL field.

  Returns the value of this URLConnection's URL
field.
Returns: the value of this URLConnection's URL field.
See Also: URLConnection.url,

  Returns the value of this URLConnection's useCaches field.

  Returns the value of this URLConnection's
useCaches field.
Returns: the value of this URLConnection's useCaches field.
See Also: URLConnection.setUseCaches(boolean),

  Tries to determine the content type of an object, based on the specified "file" component of a URL.

  Tries to determine the content type of an object, based
on the specified "file" component of a URL.
This is a convenience method that can be used by
subclasses that override the getContentType method.
Returns: a guess as to what the content type of the object is, based upon its file name.
Parameters:
- fname - a filename.
See Also: URLConnection.getContentType(),

  Tries to determine the type of an input stream based on the characters at the beginning of the input stream.

  Tries to determine the type of an input stream based on the characters at the beginning of the input stream. This method can be used by subclasses that override the getContentType method.

Ideally, this routine would not be needed. But many http servers return the incorrect content type; in addition, there are many nonstandard extensions. Direct inspection of the bytes to determine the content type is often more accurate than believing the content type claimed by the http server.
Returns: a guess at the content type, or null if none can be determined.
Parameters:
- is - an input stream that supports marks.
Throws:
- IOException - if an I/O error occurs while reading the input stream.
See Also: InputStream.mark(int), InputStream.markSupported(), URLConnection.getContentType(),

  Set the value of the allowUserInteraction field of this URLConnection.

  Set the value of the allowUserInteraction field of
this URLConnection.
Parameters:
- allowuserinteraction - the new value.
Throws:
- IllegalStateException - if already connected
See Also: URLConnection.getAllowUserInteraction(),

  Sets a specified timeout value, in milliseconds, to be used when opening a communications link to the resource referenced by this URLConnection.

  Sets a specified timeout value, in milliseconds, to be used when opening a communications link to the resource referenced by this URLConnection. If the timeout expires before the connection can be established, a java.net.SocketTimeoutException is raised. A timeout of zero is interpreted as an infinite timeout.

Some non-standard implmentation of this method may ignore the specified timeout. To see the connect timeout set, please call getConnectTimeout().
Parameters:
- timeout - an int that specifies the connect timeout value in milliseconds
Throws:
- IllegalArgumentException - if the timeout parameter is negative
Since: 1.5
See Also: URLConnection.getConnectTimeout(), URLConnection.connect(),

  Sets the ContentHandlerFactory of an application.

  Sets the ContentHandlerFactory of an application. It can be called at most once by an application.

The ContentHandlerFactory instance is used to construct a content handler from a content type

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 factory has already been defined.
- SecurityException - if a security manager exists and its checkSetFactory method doesn't allow the operation.
See Also: ContentHandlerFactory, URLConnection.getContent(), SecurityManager.checkSetFactory(),

  Sets the default value of the allowUserInteraction field for all future URLConnection objects to the specified value.

  Sets the default value of the
allowUserInteraction field for all future
URLConnection objects to the specified value.
Parameters:
- defaultallowuserinteraction - the new value.
See Also: URLConnection.getDefaultAllowUserInteraction(),

  Sets the default value of a general request property.

  Sets the default value of a general request property. When a
URLConnection is created, it is initialized with
these properties.
Parameters:
- key - the keyword by which the request is known (e.g., "accept").
- value - the value associated with the key.
See Also: URLConnection.setRequestProperty(java.lang.String,java.lang.String), URLConnection.getDefaultRequestProperty(java.lang.String),

  Sets the default value of the useCaches field to the specified value.

  Sets the default value of the useCaches field to the
specified value.
Parameters:
- defaultusecaches - the new value.
See Also: URLConnection.getDefaultUseCaches(),

  Sets the value of the doInput field for this URLConnection to the specified value.

  Sets the value of the doInput field for this URLConnection to the specified value.

A URL connection can be used for input and/or output. Set the DoInput flag to true if you intend to use the URL connection for input, false if not. The default is true.
Parameters:
- doinput - the new value.
Throws:
- IllegalStateException - if already connected
See Also: URLConnection.doInput, URLConnection.getDoInput(),

  Sets the value of the doOutput field for this URLConnection to the specified value.

  Sets the value of the doOutput field for this URLConnection to the specified value.

A URL connection can be used for input and/or output. Set the DoOutput flag to true if you intend to use the URL connection for output, false if not. The default is false.
Parameters:
- dooutput - the new value.
Throws:
- IllegalStateException - if already connected
See Also: URLConnection.getDoOutput(),

  Sets the FileNameMap.

  Sets the FileNameMap.

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:
- map - the FileNameMap to be set
Throws:
- SecurityException - if a security manager exists and its checkSetFactory method doesn't allow the operation.
Since: 1.2
See Also: SecurityManager.checkSetFactory(), URLConnection.getFileNameMap(),

  Sets the value of the ifModifiedSince field of this URLConnection to the specified value.

  Sets the value of the ifModifiedSince field of
this URLConnection to the specified value.
Parameters:
- ifmodifiedsince - the new value.
Throws:
- IllegalStateException - if already connected
See Also: URLConnection.getIfModifiedSince(),

  Sets the read timeout to a specified timeout, in milliseconds.

  Sets the read timeout to a specified timeout, in milliseconds. A non-zero value specifies the timeout when reading from Input stream when a connection is established to a resource. If the timeout expires before there is data available for read, a java.net.SocketTimeoutException is raised. A timeout of zero is interpreted as an infinite timeout.

Some non-standard implementation of this method ignores the specified timeout. To see the read timeout set, please call getReadTimeout().
Parameters:
- timeout - an int that specifies the timeout value to be used in milliseconds
Throws:
- IllegalArgumentException - if the timeout parameter is negative
Since: 1.5
See Also: URLConnection.getReadTimeout(), InputStream.read(),

  Sets the general request property.

  Sets the general request property. If a property with the key already exists, overwrite its value with the new value.

NOTE: HTTP requires all request properties which can legally have multiple instances with the same key to use a comma-seperated list syntax which enables multiple properties to be appended into a single property.
Parameters:
- key - the keyword by which the request is known (e.g., "accept").
- value - the value associated with it.
Throws:
- IllegalStateException - if already connected
- NullPointerException - if key is null
See Also: URLConnection.getRequestProperty(java.lang.String),

  Sets the value of the useCaches field of this URLConnection to the specified value.

  Sets the value of the useCaches field of this URLConnection to the specified value.

Some protocols do caching of documents. Occasionally, it is important to be able to "tunnel through" and ignore the caches (e.g., the "reload" button in a browser). If the UseCaches flag on a connection is true, the connection is allowed to use whatever caches it can. If false, caches are to be ignored. The default value comes from DefaultUseCaches, which defaults to true.
Parameters:
- usecaches - a boolean indicating whether or not to allow caching
Throws:
- IllegalStateException - if already connected
See Also: URLConnection.getUseCaches(),

  Returns a String representation of this URL connection.

  Returns a String representation of this URL connection.
Returns: a string representation of this URLConnection.