/*
 * @(#)AttributeSet.java	1.6 01/12/03
 *
 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package javax.print.attribute;

/**
 * Interface AttributeSet specifies the interface for a set of printing 
 * attributes. A printing attribute is an object whose class implements 
 * interface {@link Attribute Attribute}. 
 * <P>
 * An attribute set contains a group of <I>attribute values,</I>
 * where duplicate values are not allowed in the set.
 * Furthermore, each value in an attribute set is  
 * a member of some <I>category,</I> and at most one value in any particular 
 * category is allowed in the set. For an attribute set, the values are {@link 
 * Attribute Attribute} objects, and the categories are {@link java.lang.Class 
 * Class} objects. An attribute's category is the class (or interface) at the 
 * root of the class hierarchy for that kind of attribute. Note that an 
 * attribute object's category may be a superclass of the attribute object's 
 * class rather than the attribute object's class itself. An attribute
 * object's 
 * category is determined by calling the {@link Attribute#getCategory() 
 * <CODE>getCategory()</CODE>} method defined in interface {@link Attribute 
 * Attribute}. 
 * <P>
 * The interfaces of an AttributeSet resemble those of the Java Collections
 * API's java.util.Map interface, but is more restrictive in the types
 * it will accept, and combines keys and values into an Attribute.
 * <P>
 * Attribute sets are used in several places in the Print Service API. In 
 * each context, only certain kinds of attributes are allowed to appear in the 
 * attribute set, as determined by the tagging interfaces which the attribute 
 * class implements -- {@link DocAttribute DocAttribute}, {@link 
 * PrintRequestAttribute PrintRequestAttribute}, {@link PrintJobAttribute 
 * PrintJobAttribute}, and {@link PrintServiceAttribute
 * PrintServiceAttribute}. 
 * There are four specializations of an attribute set that are restricted to 
 * contain just one of the four kinds of attribute -- {@link DocAttributeSet 
 * DocAttributeSet}, {@link PrintRequestAttributeSet
 * PrintRequestAttributeSet}, 
 * {@link PrintJobAttributeSet PrintJobAttributeSet}, and {@link 
 * PrintServiceAttributeSet PrintServiceAttributeSet}, respectively. Note that 
 * many attribute classes implement more than one tagging interface and so may 
 * appear in more than one context. 
 * <UL>
 * <LI>
 * A {@link DocAttributeSet DocAttributeSet}, containing {@link DocAttribute 
 * DocAttribute}s, specifies the characteristics of an individual doc and the 
 * print job settings to be applied to an individual doc. 
 * <P>
 * <LI>
 * A {@link PrintRequestAttributeSet PrintRequestAttributeSet}, containing 
 * {@link PrintRequestAttribute PrintRequestAttribute}s, specifies the
 * settings 
 * to be applied to a whole print job and to all the docs in the print job. 
 * <P>
 * <LI>
 * A {@link PrintJobAttributeSet PrintJobAttributeSet}, containing {@link 
 * PrintJobAttribute PrintJobAttribute}s, reports the status of a print job. 
 * <P>
 * <LI>
 * A {@link PrintServiceAttributeSet PrintServiceAttributeSet}, containing 
 * {@link PrintServiceAttribute PrintServiceAttribute}s, reports the status of
 *  a Print Service instance. 
 * </UL>
 * <P>
 * In some contexts, the client is only allowed to examine an attribute set's 
 * contents but not change them (the set is read-only). In other places, the 
 * client is allowed both to examine and to change an attribute set's contents 
 * (the set is read-write). For a read-only attribute set, calling a mutating 
 * operation throws an UnmodifiableSetException. 
 * <P>
 * The Print Service API provides one implementation of interface 
 * AttributeSet, class {@link HashAttributeSet HashAttributeSet}.
 * A client can use class {@link 
 * HashAttributeSet HashAttributeSet} or provide its own implementation of 
 * interface AttributeSet. The Print Service API also provides 
 * implementations of interface AttributeSet's subinterfaces -- classes {@link 
 * HashDocAttributeSet HashDocAttributeSet},
 * {@link HashPrintRequestAttributeSet 
 * HashPrintRequestAttributeSet}, {@link HashPrintJobAttributeSet 
 * HashPrintJobAttributeSet}, and {@link HashPrintServiceAttributeSet 
 * HashPrintServiceAttributeSet}. 
 * <P>
 *
 * @author  Alan Kaminsky
 */
public interface AttributeSet {


    /**
     * Returns the attribute value which this attribute set contains in the 
     * given attribute category. Returns <tt>null</tt> if this attribute set 
     * does not contain any attribute value in the given attribute category.
     *
     * @param  category  Attribute category whose associated attribute value
     *                   is to be returned. It must be a
     *                   {@link java.lang.Class Class}
     *                   that implements interface {@link Attribute 
     *                   Attribute}. 
     *
     * @return  The attribute value in the given attribute category contained
     *          in this attribute set, or <tt>null</tt> if this attribute set
     *          does not contain any attribute value in the given attribute
     *          category. 
     * 
     * @throws  NullPointerException
     *     (unchecked exception) Thrown if the <CODE>category</CODE> is null.
     * @throws  ClassCastException
     *     (unchecked exception) Thrown if the <CODE>category</CODE> is not a 
     *     {@link java.lang.Class Class} that implements interface {@link 
     *     Attribute Attribute}. 
     */
    public Attribute get(Class category);

    /**
     * Adds the specified attribute to this attribute set if it is not 
     * already present, first removing any existing value in the same
     * attribute category as the specified attribute value. 
     *
     * @param  attribute  Attribute value to be added to this attribute set.
     *
     * @return  <tt>true</tt> if this attribute set changed as a result of the
     *          call, i.e., the given attribute value was not already a member 
     *          of this attribute set. 
     * 
     * @throws  NullPointerException
     *     (unchecked exception) Thrown if the <CODE>attribute</CODE> is null. 
     * @throws  UnmodifiableSetException
     *     (unchecked exception) Thrown if this attribute set does not support 
     *     the <CODE>add()</CODE> operation. 
     */
    public boolean add(Attribute attribute);


    /**
     * Removes any attribute for this category from this attribute set if  
     * present. If <CODE>category</CODE> is null, then 
     * <CODE>remove()</CODE> does nothing and returns <tt>false</tt>. 
     *
     * @param  category Attribute category to be removed from this
     *                  attribute set.
     *
     * @return  <tt>true</tt> if this attribute set changed as a result of the
     *         call, i.e., the given attribute value had been a member of this 
     *          attribute set. 
     * 
     * @throws  UnmodifiableSetException
     *     (unchecked exception) Thrown if this attribute set does not support 
     *     the <CODE>remove()</CODE> operation. 
     */
    public boolean remove(Class category);

    /**
     * Removes the specified attribute from this attribute set if  
     * present. If <CODE>attribute</CODE> is null, then 
     * <CODE>remove()</CODE> does nothing and returns <tt>false</tt>. 
     *
     * @param  attribute Attribute value to be removed from this attribute set.
     *
     * @return  <tt>true</tt> if this attribute set changed as a result of the
     *         call, i.e., the given attribute value had been a member of this 
     *          attribute set. 
     * 
     * @throws  UnmodifiableSetException
     *     (unchecked exception) Thrown if this attribute set does not support 
     *     the <CODE>remove()</CODE> operation. 
     */
    public boolean remove(Attribute attribute);

    /**
     * Returns <tt>true</tt> if this attribute set contains an 
     * attribute for the specified category.
     *
     * @param  category whose presence in this attribute set is
     *            to be tested.
     *
     * @return  <tt>true</tt> if this attribute set contains an attribute 
     *         value for the specified category.
     */
    public boolean containsKey(Class category);

    /**
     * Returns <tt>true</tt> if this attribute set contains the given  
     * attribute value.
     *
     * @param  attribute  Attribute value whose presence in this
     * attribute set is to be tested.
     *
     * @return  <tt>true</tt> if this attribute set contains the given 
     *      attribute  value.
     */
    public boolean containsValue(Attribute attribute);
        
    /**
     * Adds all of the elements in the specified set to this attribute.
     * The outcome is the same as if the =
     * {@link #add(Attribute) <CODE>add(Attribute)</CODE>} 
     * operation had been applied to this attribute set successively with each 
     * element from the specified set.
     * The behavior of the <CODE>addAll(AttributeSet)</CODE>
     * operation is unspecified if the specified set is modified while
     * the operation is in progress.
     * <P>
     * If the <CODE>addAll(AttributeSet)</CODE> operation throws an exception,
     * the effect on this attribute set's state is implementation dependent;
     * elements from the specified set before the point of the exception may
     * or may not have been added to this attribute set. 
     *
     * @param  attributes  whose elements are to be added to this attribute 
     *            set.
     *
     * @return  <tt>true</tt> if this attribute set changed as a result of the
     *          call.
     * 
     * @throws  UnmodifiableSetException
     *     (Unchecked exception) Thrown if this attribute set does not support 
     *     the <tt>addAll(AttributeSet)</tt> method. 
     * @throws  NullPointerException
     *     (Unchecked exception) Thrown if some element in the specified 
     *     set is null.
     *
     * @see #add(Attribute)
     */
    public boolean addAll(AttributeSet attributes);

    /**
     * Returns the number of attributes in this attribute set. If this
     * attribute set contains more than <tt>Integer.MAX_VALUE</tt> elements,
     * returns  <tt>Integer.MAX_VALUE</tt>.
     *
     * @return  The number of attributes in this attribute set.
     */
    public int size();
    
    /**
     * Returns an array of the attributes contained in this set.
     * @return the Attributes contained in this set as an array, zero length
     * if the AttributeSet is empty.
     */
    public Attribute[] toArray();


    /**
     * Removes all attributes from this attribute set.
     *
     * @throws  UnmodifiableSetException
     *   (unchecked exception) Thrown if this attribute set does not support 
     *     the <CODE>clear()</CODE> operation. 
     */
    public void clear();

    /**
     * Returns true if this attribute set contains no attributes.
     *
     * @return true if this attribute set contains no attributes.
     */
    public boolean isEmpty();

    /**
     * Compares the specified object with this attribute set for equality. 
     * Returns <tt>true</tt> if the given object is also an attribute set and 
     * the two attribute sets contain the same attribute category-attribute 
     * value mappings. This ensures that the 
     * <tt>equals()</tt> method works properly across different  
     * implementations of the AttributeSet interface. 
     *
     * @param  object to be compared for equality with this attribute set.
     *
     * @return  <tt>true</tt> if the specified object is equal to this 
     *       attribute   set.
     */
    public boolean equals(Object object);

    /**
     * Returns the hash code value for this attribute set. The hash code of an 
     * attribute set is defined to be the sum of the hash codes of each entry  
     * in the AttributeSet. 
     * This ensures that <tt>t1.equals(t2)</tt> implies that 
     * <tt>t1.hashCode()==t2.hashCode()</tt> for any two attribute sets 
     * <tt>t1</tt> and <tt>t2</tt>, as required by the general contract of 
     * {@link java.lang.Object#hashCode() <CODE>Object.hashCode()</CODE>}. 
     *
     * @return  The hash code value for this attribute set.
     */
    public int hashCode();

}
