1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 *
19 */
20 package org.apache.directory.mavibot.btree.comparator;
21
22
23 import java.util.Comparator;
24
25
26 /**
27 * Compares Strings
28 *
29 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
30 */
31 public class StringComparator implements Comparator<String>
32 {
33 /** A static instance of a StringComparator */
34 public static final StringComparator INSTANCE = new StringComparator();
35
36 /**
37 * A private constructor of the StringComparator class
38 */
39 private StringComparator()
40 {
41 }
42
43
44 /**
45 * Compare two Strings.
46 *
47 * @param string1 First String
48 * @param string2 Second String
49 * @return 1 if string1 > String2, 0 if string1 == String2, -1 if string1 < String2
50 */
51 public int compare( String string1, String string2 )
52 {
53 if ( string1 == string2 )
54 {
55 return 0;
56 }
57
58 if ( string1 == null )
59 {
60 return -1;
61 }
62 else if ( string2 == null )
63 {
64 return 1;
65 }
66
67 int result = string1.compareTo( string2 );
68
69 if ( result < 0 )
70 {
71 return -1;
72 }
73 else if ( result > 0 )
74 {
75 return 1;
76 }
77 else
78 {
79 return 0;
80 }
81 }
82 }