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Java > Open Source Codes > com > google > gwt > dev > util > FileOracle


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.dev.util;
17
18 import java.net.URL JavaDoc;
19
20 /**
21  * An abstraction for finding and retrieving a set of URLs by logical name.
22  * Intuitively, it works like a jar in that each URL is uniquely located
23  * somewhere in an abstract namespace. The abstract names must be constructed
24  * from a series of zero or more valid Java identifiers followed the '/'
25  * character and finally ending in a valid filename, for example,
26  * "com/google/gwt/blah.txt". Each contained abstract path corresponds to a
27  * physical URL.
28  */
29 public abstract class FileOracle {
30
31   /**
32    * Finds a URL by abstract path.
33    *
34    * @param abstractPath the abstract path of the URL to find.
35    * @return the physical URL of the contained URL, or <code>null</code> the
36    * abstract path does not refer to a contained URL.
37    */
38   public abstract URL JavaDoc find(String JavaDoc abstractPath);
39
40   /**
41    * Gets the abstract path for every URL indexed by this FileOracle. Elements
42    * of the result set can be passed into {@link #find(String)} to retrieve the
43    * physical URL.
44    *
45    * @return the abstract path of every URL indexed by this FileOracle
46    */
47   public abstract String JavaDoc[] getAllFiles();
48
49   /**
50    * Tests if this FileOracle has URLs.
51    *
52    * @return <tt>true</tt> if this list has no elements; <tt>false</tt>
53    * otherwise.
54    */
55   public abstract boolean isEmpty();
56
57 }
58
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