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Java > Open Source Codes > com > google > gwt > json > client > JSONNull


1 /*
2  * Copyright 2006 Google Inc.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
5  * use this file except in compliance with the License. You may obtain a copy of
6  * 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, WITHOUT
12  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13  * License for the specific language governing permissions and limitations under
14  * the License.
15  */
16 package com.google.gwt.json.client;
17
18 /**
19  * Represents the JSON <code>null</code> value.
20  */
21 public class JSONNull extends JSONValue {
22
23   private static final JSONNull instance = new JSONNull();
24
25   /**
26    * Returns the singleton null-valued JSON object.
27    */
28   public static JSONNull getInstance() {
29     return instance;
30   }
31
32   /**
33    * There should only be one null value.
34    */
35   private JSONNull() {
36   }
37
38   /**
39    * Returns <code>this</code>, as this is a JSONNull.
40    */
41   public JSONNull isNull() {
42     return this;
43   }
44
45   /**
46    * Returns "null" to allow for formatting <code>null</code> values.
47    */
48   public String JavaDoc toString() {
49     return "null";
50   }
51
52 }
53
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