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1   /**
2    * Copyright (c) 2008-2011, http://www.snakeyaml.org
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  
17  package org.yaml.snakeyaml.scanner;
18  
19  import org.yaml.snakeyaml.tokens.Token;
20  
21  /**
22   * This interface represents an input stream of {@link Token Tokens}.
23   * <p>
24   * The parser and the scanner form together the 'Parse' step in the loading
25   * process (see chapter 3.1 of the <a href="http://yaml.org/spec/1.1/">YAML
26   * Specification</a>).
27   * </p>
28   * 
29   * @see org.yaml.snakeyaml.tokens.Token
30   */
31  public interface Scanner {
32  
33      /**
34       * Check if the next token is one of the given types.
35       * 
36       * @param choices
37       *            token IDs.
38       * @return <code>true</code> if the next token can be assigned to a variable
39       *         of at least one of the given types. Returns <code>false</code> if
40       *         no more tokens are available.
41       * @throws ScannerException
42       *             Thrown in case of malformed input.
43       */
44      boolean checkToken(Token.ID... choices);
45  
46      /**
47       * Return the next token, but do not delete it from the stream.
48       * 
49       * @return The token that will be returned on the next call to
50       *         {@link #getToken}
51       * @throws ScannerException
52       *             Thrown in case of malformed input.
53       */
54      Token peekToken();
55  
56      /**
57       * Returns the next token.
58       * <p>
59       * The token will be removed from the stream.
60       * </p>
61       * 
62       * @throws ScannerException
63       *             Thrown in case of malformed input.
64       */
65      Token getToken();
66  }