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 Provides classes and interfaces
 that describe the types of Java<sup><font size="-2">TM</font></sup> Print
 Service attributes and how they can be collected into attribute sets.
 <P>
 <H3>What is an Attribute?</H3>
 When setting up a print job,
 a client specifies two things:
 <B>print data</B> and <B>processing instructions.</B>
 The print data is the actual content to be printed.
 The processing instructions tell the printer how to print the print data,
 such as: what media to use, how many copies to print, and
 whether to print on one or both sides of a sheet.  The client specifies
 these processing instructions with the attribute definitions of the Java
 Print Service API.
 <P>
 The print data and the processing instructions
 are separate entities.  This means that:
 <ul>
 <li>You can print the same print data
 at different times using different processing instructions.
 <br>
 For example, you can print a slide presentation
 on US letter-sized white paper,
 double-sided, stapled, 20 copies
 to make handouts for a talk;
 and you could print the same slide presentation
 on US letter-sized transparencies,
 single-sided, one copy
 to make the actual slides for the talk.
 <li>You can use the same processing instructions
 at different times to print different data.
 For example, you could set your default processing
 instructions to: US letter-sized paper, double sided, stapled.
 Whenever you print a job, it prints with these settings,
 unless you explicitly override them.
 </ul>
 <P>

 The processing instruction does not specify how the print job
 processes the request; each processing instruction is only a description
 of the results of a print job.  The print job determines the manner in
 which it achieves the results specified by the processing instructions.
 Representing processing instructions as descriptive items
 provides more flexibility for implementing print jobs.
 <P>
 <h4>Attribute Categories and Values</h4>
 Each printer has a set of capabilities, such as the ability to print on
 different paper sizes or the ability to print more than one copy.  Each of
 the capabilities has a range of values.  For example, a printer's orientation
 capability might have this range of values: [landscape, portrait].
 For each print request, the capability is set to one of these values.  The
 Java Print Service API uses the term <b>attribute category</b> to refer to
 a printer capability and the term <b>attribute value</b> to refer to the value
 of the capability.
 <p>
 In the Java Print Service API, an attribute category is represented by a Java
 class implementing the <a href="Attribute.html">Attribute</a> interface.
 Attribute values are instances of such a class or
 one of its subclasses.  For example, to specify the number of copies, an
 application constructs an instance of the
 <a href="standard/Copies.html">Copies</a> class with the
 number of desired copies and uses the <code>Copies</code> instance as part of
 the print request.  In this case, the <code>Copies</code> class represents the
 attribute category, and the <code>Copies</code> instance represents the
 attribute value.

 <h4><a name="role"></a>Attribute Roles</h4>

 When submitting a print job to a printer, the client provides the
 attributes describing the characteristics of the print data, such as
 the document name, and how the print data should be printed, such as
 double-sided, five copies.  If a print job consists of multiple
 pieces of print data, different pieces might have different processing
 instructions, such as 8 x 11 inch media for the first document, and
 11 x 17 inch media for another document.
 <p>
 Once the printer starts processing the print job,
 additional information about the job becomes available, which might include:
 the job state (such as <i>completed</i> or <i>queued</i>) and
 the number of pages printed so far.  These pieces of information are also
 attributes.  Attributes can also describe the printer itself, such as:
 the printer name, the printer location, and the number of jobs queued.
 <p>

 The Java Print Service API defines these different kinds of attributes
 with five subinterfaces of <code>Attribute</code>:
 <ul>
 <li><A HREF="DocAttribute.html">DocAttribute</A> specifies a characteristic
 of an individual document and the print job settings to be applied to an
 individual document.
 <li><A HREF="PrintRequestAttribute.html">PrintRequestAttribute</A> specifies
 a setting applied to a whole print job and to all the documents in
 the print job.
 <li><A HREF="PrintJobAttribute.html">PrintJobAttribute</A> reports the status
 of a print job.
 <li><A HREF="PrintServiceAttribute.html">PrintServiceAttribute</A> reports the
 status of a print service.
 <li><A HREF="SupportedValuesAttribute.html">SupportedValuesAttribute</A> gives
 the supported values for another attribute.
 </ul>
 Each attribute class
 implements one or more of these tagging subinterfaces
 to indicate where the attribute can be used in the API.
 If an attribute class implements multiple tagging subinterfaces,
 the attribute can be used in multiple contexts.  For example, the media
 attribute can apply to one document in a print job as a <code>DocAttribute</code>
 or to an entire print job as a <code>PrintRequestAttribute</code>.
 Certain low-level attributes
 are never used on their own
 but are always aggregated into higher-level attributes.
 These low-level attribute classes only
 implement interface <A HREF="Attribute.html">Attribute</A>,
 not any of the tagging subinterfaces.
 <P>
 The Java Print Service API defines a group of
 standard attribute classes modeled upon the attributes in
 the Internet Printing Protocol (IPP) version 1.1. The
 standard attribute classes are in the subpackage
 javax.print.attribute.standard to keep the actual
 attribute classes conceptually separate from the generic
 apparatus defined in package javax.print.attribute.

 <H3>Attribute Sets</H3>
 A client usually needs to provide more than one processing
 instruction when submitting a print job.  For example, the client might need to
 specify a media size of A4 and a landscape orientation.  To send more than one
 processing instruction, the client collects the attributes into an
 attribute set, which the Java Print Service API represents with the
 <a href="AttributeSet.html">AttributeSet</a>
  interface.
 <p>
 The <code>AttributeSet</code> interface is similar to the
 <a href="../../../java/util/Map.html">Map</a> interface: it provides a map of
 key to values, in which each key is unique and can contain no more than one
 value.  However, the <code>AttributeSet</code> interface is designed to
 specifically support the needs of the Java Print Service API.  An
 <code>AttributeSet</code> requires that:
 <OL TYPE=1>
 <LI>Each key in an <code>AttributeSet</code> corresponds to a category, and
 the value of the key can only be one of the attribute values that belong
 to the category represented by the key.  Thus, unlike a <code>Map</code>, an
 <code>AttributeSet</code> restricts the possible values of a key: an
 attribute category cannot be set to an attribute value that does not belong to
 that category.
 <LI>No two attributes from the same category can exist in the same set.
 For example, an attribute collection
 must not contain both a "one-sided" attribute and a "two-sided" attribute
 because these two attributes give the printer conflicting instructions.
 <LI>Only attributes implementing the <code>Attribute</code> interface can
 be added to the set.
 </OL>

 <P>
 The javax.print.attribute package includes
 <A HREF="HashAttributeSet.html">HashAttributeSet</A>
 as a concrete implementation of the attribute set interface.
 <code>HashAttributeSet</code> provides an attribute set based on a hash map.
 You can use this implementation or provide your own implementation
 of interface <code>AttributeSet</code>.
 <p>
 The Java Print Service API provides four specializations of an attribute set
 that are restricted to contain just one of the four kinds of attributes,
 as discussed in the <a href="#role">Attribute Roles</a> section:
 <ul>
 <li><A HREF="DocAttributeSet.html">DocAttributeSet</A>
 <li><A HREF="PrintRequestAttributeSet.html">PrintRequestAttributeSet</A>
 <li><A HREF="PrintJobAttributeSet.html">PrintJobAttributeSet</A>
 <li><A HREF="PrintServiceAttributeSet.html">PrintServiceAttributeSet</A>
 </ul>
 Notice that only four kinds of attribute sets are listed here, but there are
 five kinds of attributes.  Interface
 <A HREF="SupportedValuesAttribute.html">SupportedValuesAttribute</A>
 denotes an attribute that gives the supported values for another attribute.
 Supported-values attributes are never aggregated into attribute sets,
 so there is no attribute set subinterface defined for them.

 <P>
 In some contexts, an attribute set is read-only, which means that the
 client is only allowed to examine an attribute set's
 contents but not change them. In other contexts, the attribute set is read-write,
 which means that the client is allowed both to examine and to change an
 attribute set's contents. For a read-only attribute set, calling a mutating
 operation throws an <code>UnmodifiableSetException</code>.
 <P>
 Package javax.print.attribute includes
 one concrete implementation of each of the attribute set subinterfaces:
 <ul>
 <li><A HREF="HashDocAttributeSet.html">HashDocAttributeSet</A>
 <li><A HREF="HashPrintRequestAttributeSet.html">HashPrintRequestAttributeSet</A>,
 <li><A HREF="HashPrintJobAttributeSet.html">HashPrintJobAttributeSet</A>,
 <li><A HREF="HashPrintServiceAttributeSet.html">HashPrintServiceAttributeSet</A>.
 </ul>
 All of these classes extend <A HREF="HashAttributeSet.html">HashAttributeSet</A>
 and enforce the restriction that the attribute set is only allowed to contain
 the corresponding kind of attribute.
 <P>
 <H3>Attribute Class Design</H3>
 An attribute value is a small, atomic data item,
 such as an integer or an enumerated value.  The Java Print Service API
 does not use primitive data types, such as int, to represent attribute
 values for these reasons:
 <ul>
 <li>Primitive data types are not type-safe.  For example, a compiler
 should not allow a "copies" attribute value to
 be used for a "sides" attribute.
 <li>Some attributes must be represented as a record of several
 values.  One example is printer resolution, which requires two
 numbers, such as 600 and 300 representing 600 x 300 dpi.
 </ul>
 For type-safety and to represent all attributes uniformly, the Java
 Print Service API defines each attribute category as a class, such as
 class <code>Copies</code>, class <a href="standard/Sides.html">Sides</a>, and class
 <a href="standard/PrinterResolution.html">PrinterResolution</a>.  Each
 attribute class wraps one or more primitive data items containing the
 attribute's value.  Attribute set operations perform frequent
 comparisons between attribute category objects when adding attributes,
 finding existing attributes in the same category, and looking
 up an attribute given its category.  Because an attribute category is
 represented by a class, fast attribute-value comparisons can be performed
 with the <code>Class.equals</code> method.
 <p>
 Even though the Java Print Service API includes a large number of
 different attribute categories, there are only a few different types
 of attribute values.  Most attributes can be represented by a small
 number of data types, such as: integer values, integer ranges, text,
 or an enumeration of integer values.  The type of the attribute value that
 a category accepts is called the attribute's abstract syntax.  To
 provide consistency and reduce code duplication, the Java Print Service
 API defines abstract syntax classes to represent each
 abstract syntax, and these classes are used as the parent of standard
 attributes whenever possible.  The abstract syntax classes are:
 <ul>
 <li><a href="EnumSyntax.html">EnumSyntax</a>
 provides a type-safe enumeration in which enumerated
 values are represented as singleton objects.  Each enumeration
 singleton is an instance of the enumeration class that wraps a hidden
 int value.
 <li><a href="IntegerSyntax.html">IntegerSyntax</a>
  is the abstract syntax for integer-valued attributes.
 <li><a href="TextSyntax.html">TextSyntax</a> is
 the abstract syntax for text-valued attributes, and
 includes a locale giving the text string's natural language.
 <li><a href="SetOfIntegerSyntax.html">SetOfIntegerSyntax</a>
  is the abstract syntax for attributes
 representing a range or set of integers
 <li><a href="ResolutionSyntax.html">ResolutionSyntax</a>
  is the abstract syntax for attributes representing
  resolution values, such as 600x300 dpi.
 <li><a href="Size2DSyntax.html">Size2DSyntax</a>
  is the abstract syntax for attributes representing a
 two-dimensional size, such as a paper size of 8.5 x 11 inches.
 <li><a href="DateTimeSyntax.html">DateTimeSyntax</a>
  is the abstract syntax for attributes whose value is a date and time.
 <li><a href="URISyntax.html">URISyntax</a> is the
 abstract syntax for attributes whose value is a Uniform Resource
 Indicator.
 </ul>
 The abstract syntax classes are independent of the attributes that
 use them.  In fact, applications that have nothing to do with
 printing can use the abstract syntax classes.  Although most of the
 standard attribute classes extend one of the abstract syntax classes,
 no attribute class is required to extend one of these classes.  The
 abstract syntax classes merely provide a convenient implementation that
 can be shared by many attribute classes.
 <p>
 Each attribute class implements the <code>Attribute</code> interface, either
 directly or indirectly, to mark it as a printing attribute.  An
 attribute class that can appear in restricted attribute sets in
 certain contexts also implements one or more subinterfaces of
 <code>Attribute</code>.  Most attribute classes also extend the appropriate
 abstract syntax class to get the implementation.  Consider the
 <code>Sides</code> attribute class:
 <pre>
 <blockquote>
 public class Sides
   extends EnumSyntax
   implements DocAttribute, PrintRequestAttribute, PrintJobAttribute
   {
   public final Object getCategory()
     {
     return Sides.class;
     }
   ...
   }
 </blockquote>
 </pre>
 <p>
 Since every attribute class implements <code>Attribute</code>, every attribute
 class must provide an implementation for the
 {@link javax.print.attribute.Attribute#getCategory() getCategory} method,
 which returns the attribute category.  In the case of <code>Sides</code>, the
 <code>getCategory</code> method returns <code>Sides.class</code>.  The
 <code>getCategory</code> method is final to ensure that any vendor-defined
 subclasses of a standard attribute class appear in the same category.
 Every attribute object is immutable once constructed so that attribute object
 references can be passed around freely.  To get a different attribute
 value, construct a different attribute object.

 <h3>Attribute Vendors</h3>

 The Java Print Service API is designed so that vendors can:
 <ul>
 <li>define new vendor-specific values for any standard attribute
 defined in <a href="standard/package-summary.html">
 javax.print.attribute.standard</a>.
 <li>define new attribute categories representing the vendor printer's
 proprietary capabilities not already supported by the standard
 attributes.
 </ul>
 To define a new value for an attribute, a client can construct
 instances of such attributes with arbitrary values at runtime.
 However, an enumerated attribute using an abstract syntax class
 of <code>EnumSyntax</code> specifies all the possible attribute values
 at compile time as singleton instances of the attribute class.  This
 means that new enumerated values cannot be constructed at run time.
 To define new vendor-specific values for a standard enumerated
 attribute, the vendor must define a new attribute class specifying
 the new singleton instances.  To ensure that the new attribute values
 fall in the same category as the standard attribute values, the new
 attribute class must be a subclass of the standard attribute class.
 <p>
 To define a new attribute category, a vendor defines a new attribute
 class.  This attribute class, like the standard attribute classes,
 implements <code>Attribute</code> or one of its subinterfaces and extends an
 abstract syntax class.  The vendor can either use an existing
 abstract syntax class or define a new one.  The new vendor-defined
 attribute can be used wherever an <code>Attribute</code> is used, such as in an
 <code>AttributeSet</code>.

 <h3>Using Attributes</h3>

 A typical printing application uses the <code>PrintRequestAttributeSet</code>
 because print-request attributes are the types of attributes that
 client usually specifies.  This example demonstrates creating an attribute
 set of print-request attributes and locating a printer that can
 print the document according to the specified attributes:
 <p>
 <pre>
 <blockquote>

 FileInputStream psStream;
 try {
    psstream = new FileInputStream("file.ps");
 } catch (FileNotFoundException ffne) {
 }
 if (psstream == null) {
     return;
 }
 //Set the document type.  See the DocFlavor documentation for
 //more information.
 DocFlavor psInFormat = DocFlavor.INPUT_STREAM.POSTSCRIPT;
 Doc myDoc = new SimpleDoc(pstream, psInFormat, null);
 PrintRequestAttributeSet aset = new HashPrintRequestAttributeSet();
 aset.add(new Copies(5));
 aset.add(MediaSize.A4);
 aset.add(Sides.DUPLEX);

 PrintService[] services =
 		PrintServiceLookup.lookupPrintServices(psInFormat, aset);
 if (services.length > 0) {
    DocPrintJob job = services[0].createPrintJob();
    try {
 	job.print(myDoc, aset);
    } catch (PrintException pe) {}
 }
 </blockquote>
 </pre>
 <P>
 Please note: In the javax.print APIs, a null reference parameter to methods
 is incorrect unless explicitly documented on the method as having a meaningful
 interpretation. Usage to the contrary is incorrect coding and may result
 in a run time exception either immediately or at some later time.
 IllegalArgumentException and NullPointerException are examples of
 typical and acceptable run time exceptions for such cases.
 <P>
 @since 1.4
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	<title>javax.print.attribute package</title>
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	<body bgcolor="white">
	Provides classes and interfaces
	that describe the types of Java<sup><font size="-2">TM</font></sup> Print
	Service attributes and how they can be collected into attribute sets.
	<P>
	<H3>What is an Attribute?</H3>
	When setting up a print job,
	a client specifies two things:
	<B>print data</B> and <B>processing instructions.</B>
	The print data is the actual content to be printed.
	The processing instructions tell the printer how to print the print data,
	such as: what media to use, how many copies to print, and
	whether to print on one or both sides of a sheet. The client specifies
	these processing instructions with the attribute definitions of the Java
	Print Service API.
	<P>
	The print data and the processing instructions
	are separate entities. This means that:
	<ul>
	<li>You can print the same print data
	at different times using different processing instructions.
	<br>
	For example, you can print a slide presentation
	on US letter-sized white paper,
	double-sided, stapled, 20 copies
	to make handouts for a talk;
	and you could print the same slide presentation
	on US letter-sized transparencies,
	single-sided, one copy
	to make the actual slides for the talk.
	<li>You can use the same processing instructions
	at different times to print different data.
	For example, you could set your default processing
	instructions to: US letter-sized paper, double sided, stapled.
	Whenever you print a job, it prints with these settings,
	unless you explicitly override them.
	</ul>
	<P>

	The processing instruction does not specify how the print job
	processes the request; each processing instruction is only a description
	of the results of a print job. The print job determines the manner in
	which it achieves the results specified by the processing instructions.
	Representing processing instructions as descriptive items
	provides more flexibility for implementing print jobs.
	<P>
	<h4>Attribute Categories and Values</h4>
	Each printer has a set of capabilities, such as the ability to print on
	different paper sizes or the ability to print more than one copy. Each of
	the capabilities has a range of values. For example, a printer's orientation
	capability might have this range of values: [landscape, portrait].
	For each print request, the capability is set to one of these values. The
	Java Print Service API uses the term <b>attribute category</b> to refer to
	a printer capability and the term <b>attribute value</b> to refer to the value
	of the capability.
	<p>
	In the Java Print Service API, an attribute category is represented by a Java
	class implementing the <a href="Attribute.html">Attribute</a> interface.
	Attribute values are instances of such a class or
	one of its subclasses. For example, to specify the number of copies, an
	application constructs an instance of the
	<a href="standard/Copies.html">Copies</a> class with the
	number of desired copies and uses the <code>Copies</code> instance as part of
	the print request. In this case, the <code>Copies</code> class represents the
	attribute category, and the <code>Copies</code> instance represents the
	attribute value.

	<h4><a name="role"></a>Attribute Roles</h4>

	When submitting a print job to a printer, the client provides the
	attributes describing the characteristics of the print data, such as
	the document name, and how the print data should be printed, such as
	double-sided, five copies. If a print job consists of multiple
	pieces of print data, different pieces might have different processing
	instructions, such as 8 x 11 inch media for the first document, and
	11 x 17 inch media for another document.
	<p>
	Once the printer starts processing the print job,
	additional information about the job becomes available, which might include:
	the job state (such as <i>completed</i> or <i>queued</i>) and
	the number of pages printed so far. These pieces of information are also
	attributes. Attributes can also describe the printer itself, such as:
	the printer name, the printer location, and the number of jobs queued.
	<p>

	The Java Print Service API defines these different kinds of attributes
	with five subinterfaces of <code>Attribute</code>:
	<ul>
	<li><A HREF="DocAttribute.html">DocAttribute</A> specifies a characteristic
	of an individual document and the print job settings to be applied to an
	individual document.
	<li><A HREF="PrintRequestAttribute.html">PrintRequestAttribute</A> specifies
	a setting applied to a whole print job and to all the documents in
	the print job.
	<li><A HREF="PrintJobAttribute.html">PrintJobAttribute</A> reports the status
	of a print job.
	<li><A HREF="PrintServiceAttribute.html">PrintServiceAttribute</A> reports the
	status of a print service.
	<li><A HREF="SupportedValuesAttribute.html">SupportedValuesAttribute</A> gives
	the supported values for another attribute.
	</ul>
	Each attribute class
	implements one or more of these tagging subinterfaces
	to indicate where the attribute can be used in the API.
	If an attribute class implements multiple tagging subinterfaces,
	the attribute can be used in multiple contexts. For example, the media
	attribute can apply to one document in a print job as a <code>DocAttribute</code>
	or to an entire print job as a <code>PrintRequestAttribute</code>.
	Certain low-level attributes
	are never used on their own
	but are always aggregated into higher-level attributes.
	These low-level attribute classes only
	implement interface <A HREF="Attribute.html">Attribute</A>,
	not any of the tagging subinterfaces.
	<P>
	The Java Print Service API defines a group of
	standard attribute classes modeled upon the attributes in
	the Internet Printing Protocol (IPP) version 1.1. The
	standard attribute classes are in the subpackage
	javax.print.attribute.standard to keep the actual
	attribute classes conceptually separate from the generic
	apparatus defined in package javax.print.attribute.

	<H3>Attribute Sets</H3>
	A client usually needs to provide more than one processing
	instruction when submitting a print job. For example, the client might need to
	specify a media size of A4 and a landscape orientation. To send more than one
	processing instruction, the client collects the attributes into an
	attribute set, which the Java Print Service API represents with the
	<a href="AttributeSet.html">AttributeSet</a>
	interface.
	<p>
	The <code>AttributeSet</code> interface is similar to the
	<a href="../../../java/util/Map.html">Map</a> interface: it provides a map of
	key to values, in which each key is unique and can contain no more than one
	value. However, the <code>AttributeSet</code> interface is designed to
	specifically support the needs of the Java Print Service API. An
	<code>AttributeSet</code> requires that:
	<OL TYPE=1>
	<LI>Each key in an <code>AttributeSet</code> corresponds to a category, and
	the value of the key can only be one of the attribute values that belong
	to the category represented by the key. Thus, unlike a <code>Map</code>, an
	<code>AttributeSet</code> restricts the possible values of a key: an
	attribute category cannot be set to an attribute value that does not belong to
	that category.
	<LI>No two attributes from the same category can exist in the same set.
	For example, an attribute collection
	must not contain both a "one-sided" attribute and a "two-sided" attribute
	because these two attributes give the printer conflicting instructions.
	<LI>Only attributes implementing the <code>Attribute</code> interface can
	be added to the set.
	</OL>

	<P>
	The javax.print.attribute package includes
	<A HREF="HashAttributeSet.html">HashAttributeSet</A>
	as a concrete implementation of the attribute set interface.
	<code>HashAttributeSet</code> provides an attribute set based on a hash map.
	You can use this implementation or provide your own implementation
	of interface <code>AttributeSet</code>.
	<p>
	The Java Print Service API provides four specializations of an attribute set
	that are restricted to contain just one of the four kinds of attributes,
	as discussed in the <a href="#role">Attribute Roles</a> section:
	<ul>
	<li><A HREF="DocAttributeSet.html">DocAttributeSet</A>
	<li><A HREF="PrintRequestAttributeSet.html">PrintRequestAttributeSet</A>
	<li><A HREF="PrintJobAttributeSet.html">PrintJobAttributeSet</A>
	<li><A HREF="PrintServiceAttributeSet.html">PrintServiceAttributeSet</A>
	</ul>
	Notice that only four kinds of attribute sets are listed here, but there are
	five kinds of attributes. Interface
	<A HREF="SupportedValuesAttribute.html">SupportedValuesAttribute</A>
	denotes an attribute that gives the supported values for another attribute.
	Supported-values attributes are never aggregated into attribute sets,
	so there is no attribute set subinterface defined for them.

	<P>
	In some contexts, an attribute set is read-only, which means that the
	client is only allowed to examine an attribute set's
	contents but not change them. In other contexts, the attribute set is read-write,
	which means that the client is allowed both to examine and to change an
	attribute set's contents. For a read-only attribute set, calling a mutating
	operation throws an <code>UnmodifiableSetException</code>.
	<P>
	Package javax.print.attribute includes
	one concrete implementation of each of the attribute set subinterfaces:
	<ul>
	<li><A HREF="HashDocAttributeSet.html">HashDocAttributeSet</A>
	<li><A HREF="HashPrintRequestAttributeSet.html">HashPrintRequestAttributeSet</A>,
	<li><A HREF="HashPrintJobAttributeSet.html">HashPrintJobAttributeSet</A>,
	<li><A HREF="HashPrintServiceAttributeSet.html">HashPrintServiceAttributeSet</A>.
	</ul>
	All of these classes extend <A HREF="HashAttributeSet.html">HashAttributeSet</A>
	and enforce the restriction that the attribute set is only allowed to contain
	the corresponding kind of attribute.
	<P>
	<H3>Attribute Class Design</H3>
	An attribute value is a small, atomic data item,
	such as an integer or an enumerated value. The Java Print Service API
	does not use primitive data types, such as int, to represent attribute
	values for these reasons:
	<ul>
	<li>Primitive data types are not type-safe. For example, a compiler
	should not allow a "copies" attribute value to
	be used for a "sides" attribute.
	<li>Some attributes must be represented as a record of several
	values. One example is printer resolution, which requires two
	numbers, such as 600 and 300 representing 600 x 300 dpi.
	</ul>
	For type-safety and to represent all attributes uniformly, the Java
	Print Service API defines each attribute category as a class, such as
	class <code>Copies</code>, class <a href="standard/Sides.html">Sides</a>, and class
	<a href="standard/PrinterResolution.html">PrinterResolution</a>. Each
	attribute class wraps one or more primitive data items containing the
	attribute's value. Attribute set operations perform frequent
	comparisons between attribute category objects when adding attributes,
	finding existing attributes in the same category, and looking
	up an attribute given its category. Because an attribute category is
	represented by a class, fast attribute-value comparisons can be performed
	with the <code>Class.equals</code> method.
	<p>
	Even though the Java Print Service API includes a large number of
	different attribute categories, there are only a few different types
	of attribute values. Most attributes can be represented by a small
	number of data types, such as: integer values, integer ranges, text,
	or an enumeration of integer values. The type of the attribute value that
	a category accepts is called the attribute's abstract syntax. To
	provide consistency and reduce code duplication, the Java Print Service
	API defines abstract syntax classes to represent each
	abstract syntax, and these classes are used as the parent of standard
	attributes whenever possible. The abstract syntax classes are:
	<ul>
	<li><a href="EnumSyntax.html">EnumSyntax</a>
	provides a type-safe enumeration in which enumerated
	values are represented as singleton objects. Each enumeration
	singleton is an instance of the enumeration class that wraps a hidden
	int value.
	<li><a href="IntegerSyntax.html">IntegerSyntax</a>
	is the abstract syntax for integer-valued attributes.
	<li><a href="TextSyntax.html">TextSyntax</a> is
	the abstract syntax for text-valued attributes, and
	includes a locale giving the text string's natural language.
	<li><a href="SetOfIntegerSyntax.html">SetOfIntegerSyntax</a>
	is the abstract syntax for attributes
	representing a range or set of integers
	<li><a href="ResolutionSyntax.html">ResolutionSyntax</a>
	is the abstract syntax for attributes representing
	resolution values, such as 600x300 dpi.
	<li><a href="Size2DSyntax.html">Size2DSyntax</a>
	is the abstract syntax for attributes representing a
	two-dimensional size, such as a paper size of 8.5 x 11 inches.
	<li><a href="DateTimeSyntax.html">DateTimeSyntax</a>
	is the abstract syntax for attributes whose value is a date and time.
	<li><a href="URISyntax.html">URISyntax</a> is the
	abstract syntax for attributes whose value is a Uniform Resource
	Indicator.
	</ul>
	The abstract syntax classes are independent of the attributes that
	use them. In fact, applications that have nothing to do with
	printing can use the abstract syntax classes. Although most of the
	standard attribute classes extend one of the abstract syntax classes,
	no attribute class is required to extend one of these classes. The
	abstract syntax classes merely provide a convenient implementation that
	can be shared by many attribute classes.
	<p>
	Each attribute class implements the <code>Attribute</code> interface, either
	directly or indirectly, to mark it as a printing attribute. An
	attribute class that can appear in restricted attribute sets in
	certain contexts also implements one or more subinterfaces of
	<code>Attribute</code>. Most attribute classes also extend the appropriate
	abstract syntax class to get the implementation. Consider the
	<code>Sides</code> attribute class:
	<pre>
	<blockquote>
	public class Sides
	extends EnumSyntax
	implements DocAttribute, PrintRequestAttribute, PrintJobAttribute
	{
	public final Object getCategory()
	{
	return Sides.class;
	}
	...
	}
	</blockquote>
	</pre>
	<p>
	Since every attribute class implements <code>Attribute</code>, every attribute
	class must provide an implementation for the
	{@link javax.print.attribute.Attribute#getCategory() getCategory} method,
	which returns the attribute category. In the case of <code>Sides</code>, the
	<code>getCategory</code> method returns <code>Sides.class</code>. The
	<code>getCategory</code> method is final to ensure that any vendor-defined
	subclasses of a standard attribute class appear in the same category.
	Every attribute object is immutable once constructed so that attribute object
	references can be passed around freely. To get a different attribute
	value, construct a different attribute object.

	<h3>Attribute Vendors</h3>

	The Java Print Service API is designed so that vendors can:
	<ul>
	<li>define new vendor-specific values for any standard attribute
	defined in <a href="standard/package-summary.html">
	javax.print.attribute.standard</a>.
	<li>define new attribute categories representing the vendor printer's
	proprietary capabilities not already supported by the standard
	attributes.
	</ul>
	To define a new value for an attribute, a client can construct
	instances of such attributes with arbitrary values at runtime.
	However, an enumerated attribute using an abstract syntax class
	of <code>EnumSyntax</code> specifies all the possible attribute values
	at compile time as singleton instances of the attribute class. This
	means that new enumerated values cannot be constructed at run time.
	To define new vendor-specific values for a standard enumerated
	attribute, the vendor must define a new attribute class specifying
	the new singleton instances. To ensure that the new attribute values
	fall in the same category as the standard attribute values, the new
	attribute class must be a subclass of the standard attribute class.
	<p>
	To define a new attribute category, a vendor defines a new attribute
	class. This attribute class, like the standard attribute classes,
	implements <code>Attribute</code> or one of its subinterfaces and extends an
	abstract syntax class. The vendor can either use an existing
	abstract syntax class or define a new one. The new vendor-defined
	attribute can be used wherever an <code>Attribute</code> is used, such as in an
	<code>AttributeSet</code>.

	<h3>Using Attributes</h3>

	A typical printing application uses the <code>PrintRequestAttributeSet</code>
	because print-request attributes are the types of attributes that
	client usually specifies. This example demonstrates creating an attribute
	set of print-request attributes and locating a printer that can
	print the document according to the specified attributes:
	<p>
	<pre>
	<blockquote>

	FileInputStream psStream;
	try {
	psstream = new FileInputStream("file.ps");
	} catch (FileNotFoundException ffne) {
	}
	if (psstream == null) {
	return;
	}
	//Set the document type. See the DocFlavor documentation for
	//more information.
	DocFlavor psInFormat = DocFlavor.INPUT_STREAM.POSTSCRIPT;
	Doc myDoc = new SimpleDoc(pstream, psInFormat, null);
	PrintRequestAttributeSet aset = new HashPrintRequestAttributeSet();
	aset.add(new Copies(5));
	aset.add(MediaSize.A4);
	aset.add(Sides.DUPLEX);

	PrintService[] services =
	PrintServiceLookup.lookupPrintServices(psInFormat, aset);
	if (services.length > 0) {
	DocPrintJob job = services[0].createPrintJob();
	try {
	job.print(myDoc, aset);
	} catch (PrintException pe) {}
	}
	</blockquote>
	</pre>
	<P>
	Please note: In the javax.print APIs, a null reference parameter to methods
	is incorrect unless explicitly documented on the method as having a meaningful
	interpretation. Usage to the contrary is incorrect coding and may result
	in a run time exception either immediately or at some later time.
	IllegalArgumentException and NullPointerException are examples of
	typical and acceptable run time exceptions for such cases.
	<P>
	@since 1.4
	</body>
	</html>