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Java > Open Source Codes > org > apache > beehive > netui > script > el > parser > Token


1 /*
2  * Copyright 2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  *
16  * $Header:$
17  */
18 package org.apache.beehive.netui.script.el.parser;
19
20 /**
21  * Describes the input token stream.
22  */
23
24 public class Token {
25
26     /**
27      * An integer that describes the kind of this token. This numbering
28      * system is determined by JavaCCParser, and a table of these numbers is
29      * stored in the file ...Constants.java.
30      */
31     public int kind;
32
33     /**
34      * beginLine and beginColumn describe the position of the first character
35      * of this token; endLine and endColumn describe the position of the
36      * last character of this token.
37      */
38     public int beginLine, beginColumn, endLine, endColumn;
39
40     /**
41      * The string image of the token.
42      */
43     public String JavaDoc image;
44
45     /**
46      * A reference to the next regular (non-special) token from the input
47      * stream. If this is the last token from the input stream, or if the
48      * token manager has not read tokens beyond this one, this field is
49      * set to null. This is true only if this token is also a regular
50      * token. Otherwise, see below for a description of the contents of
51      * this field.
52      */
53     public Token next;
54
55     /**
56      * This field is used to access special tokens that occur prior to this
57      * token, but after the immediately preceding regular (non-special) token.
58      * If there are no such special tokens, this field is set to null.
59      * When there are more than one such special token, this field refers
60      * to the last of these special tokens, which in turn refers to the next
61      * previous special token through its specialToken field, and so on
62      * until the first special token (whose specialToken field is null).
63      * The next fields of special tokens refer to other special tokens that
64      * immediately follow it (without an intervening regular token). If there
65      * is no such token, this field is null.
66      */
67     public Token specialToken;
68
69     /**
70      * Returns the image.
71      */
72     public String JavaDoc toString() {
73         return image;
74     }
75
76     /**
77      * Returns a new Token object, by default. However, if you want, you
78      * can create and return subclass objects based on the value of ofKind.
79      * Simply add the cases to the switch for all those special cases.
80      * For example, if you have a subclass of Token called IDToken that
81      * you want to create if ofKind is ID, simlpy add something like :
82      * <p/>
83      * case MyParserConstants.ID : return new IDToken();
84      * <p/>
85      * to the following switch statement. Then you can cast matchedToken
86      * variable to the appropriate type and use it in your lexical actions.
87      */
88     public static final Token newToken(int ofKind) {
89         switch(ofKind) {
90             default :
91                 return new Token();
92         }
93     }
94
95 }
96
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