001: /*
002: * Copyright (c) 1998-2008 Caucho Technology -- all rights reserved
003: *
004: * This file is part of Resin(R) Open Source
005: *
006: * Each copy or derived work must preserve the copyright notice and this
007: * notice unmodified.
008: *
009: * Resin Open Source is free software; you can redistribute it and/or modify
010: * it under the terms of the GNU General Public License as published by
011: * the Free Software Foundation; either version 2 of the License, or
012: * (at your option) any later version.
013: *
014: * Resin Open Source is distributed in the hope that it will be useful,
015: * but WITHOUT ANY WARRANTY; without even the implied warranty of
016: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
017: * of NON-INFRINGEMENT. See the GNU General Public License for more
018: * details.
019: *
020: * You should have received a copy of the GNU General Public License
021: * along with Resin Open Source; if not, write to the
022: * Free SoftwareFoundation, Inc.
023: * 59 Temple Place, Suite 330
024: * Boston, MA 02111-1307 USA
025: *
026: * @author Scott Ferguson
027: */
028:
029: package com.caucho.relaxng.program;
030:
031: import com.caucho.util.L10N;
032: import com.caucho.xml.QName;
033:
034: import java.util.HashSet;
035:
036: /**
037: * Generates programs from patterns.
038: */
039: public class EmptyItem extends Item {
040: protected final static L10N L = new L10N(EmptyItem.class);
041:
042: private static final EmptyItem EMPTY = new EmptyItem();
043:
044: /**
045: * Creates the empty item.
046: */
047: public static EmptyItem create() {
048: return EMPTY;
049: }
050:
051: /**
052: * Adds to the first set, the set of element names possible.
053: */
054: public void firstSet(HashSet<QName> set) {
055: }
056:
057: /**
058: * The empty item can produce empty.
059: */
060: public boolean allowEmpty() {
061: return true;
062: }
063:
064: /**
065: * Sets an attribute.
066: *
067: * @param name the name of the attribute
068: * @param value the value of the attribute
069: *
070: * @return the program for handling the element
071: */
072: public Item setAttribute(QName name, String value) {
073: return this ;
074: }
075:
076: /**
077: * Returns the pretty printed syntax.
078: */
079: public String toSyntaxDescription(int depth) {
080: return "empty";
081: }
082:
083: /**
084: * True for simple syntax.
085: */
086: public boolean isSimpleSyntax() {
087: return true;
088: }
089:
090: /**
091: * Returns the hash code for the empty item.
092: */
093: public int hashCode() {
094: return 37;
095: }
096:
097: /**
098: * Returns true if the object is an empty item.
099: */
100: public boolean equals(Object o) {
101: return o instanceof EmptyItem;
102: }
103:
104: public String toString() {
105: return "EmptyItem[]";
106: }
107: }
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