1 /*

     2  * Copyright (c) 2002, 2004, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package sun.misc;

    27 

    28 import java.util.Comparator;

    29 

    30 /** Implements a locale and case insensitive comparator suitable for

    31     strings that are known to only contain ASCII characters. Some

    32     tables internal to the JDK contain only ASCII data and are using

    33     the "generalized" java.lang.String case-insensitive comparator

    34     which converts each character to both upper and lower case. */

    35 

    36 public class ASCIICaseInsensitiveComparator implements Comparator<String> {

    37     public static final Comparator<String> CASE_INSENSITIVE_ORDER =

    38         new ASCIICaseInsensitiveComparator();

    39 

    40     public int compare(String s1, String s2) {

    41         int n1=s1.length(), n2=s2.length();

    42         int minLen = n1 < n2 ? n1 : n2;

    43         for (int i=0; i < minLen; i++) {

    44             char c1 = s1.charAt(i);

    45             char c2 = s2.charAt(i);

    46             assert c1 <= '\u007F' && c2 <= '\u007F';

    47             if (c1 != c2) {

    48                 c1 = (char)toLower(c1);

    49                 c2 = (char)toLower(c2);

    50                 if (c1 != c2) {

    51                     return c1 - c2;

    52                 }

    53             }

    54         }

    55         return n1 - n2;

    56     }

    57 

    58     /**

    59      * A case insensitive hash code method to go with the case insensitive

    60      * compare() method.

    61      *

    62      * Returns a hash code for this ASCII string as if it were lower case.

    63      *

    64      * returns same answer as:<p>

    65      * <code>s.toLowerCase(Locale.US).hashCode();</code><p>

    66      * but does not allocate memory (it does NOT have the special

    67      * case Turkish rules).

    68      *

    69      * @param s a String to compute the hashcode on.

    70      * @return  a hash code value for this object.

    71      */

    72     public static int lowerCaseHashCode(String s) {

    73         int h = 0;

    74         int len = s.length();

    75 

    76         for (int i = 0; i < len; i++) {

    77             h = 31*h + toLower(s.charAt(i));

    78         }

    79 

    80         return h;

    81     }

    82 

    83     /* If java.util.regex.ASCII ever becomes public or sun.*, use its code instead:*/

    84     static boolean isLower(int ch) {

    85         return ((ch-'a')|('z'-ch)) >= 0;

    86     }

    87 

    88     static boolean isUpper(int ch) {

    89         return ((ch-'A')|('Z'-ch)) >= 0;

    90     }

    91 

    92     static int toLower(int ch) {

    93         return isUpper(ch) ? (ch + 0x20) : ch;

    94     }

    95 

    96     static int toUpper(int ch) {

    97         return isLower(ch) ? (ch - 0x20) : ch;

    98     }

    99 }