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      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 }
    100