StringUtil2.java

package com.wangyin.ak47.common;


/**
 * String-related helper class
 * 
 * @author hannyu
 *
 */
public class StringUtil2 {
    
    
    private static final char[] lowercases = {
          '\000','\001','\002','\003','\004','\005','\006','\007',
          '\010','\011','\012','\013','\014','\015','\016','\017',
          '\020','\021','\022','\023','\024','\025','\026','\027',
          '\030','\031','\032','\033','\034','\035','\036','\037',
          '\040','\041','\042','\043','\044','\045','\046','\047',
          '\050','\051','\052','\053','\054','\055','\056','\057',
          '\060','\061','\062','\063','\064','\065','\066','\067',
          '\070','\071','\072','\073','\074','\075','\076','\077',
          '\100','\141','\142','\143','\144','\145','\146','\147',
          '\150','\151','\152','\153','\154','\155','\156','\157',
          '\160','\161','\162','\163','\164','\165','\166','\167',
          '\170','\171','\172','\133','\134','\135','\136','\137',
          '\140','\141','\142','\143','\144','\145','\146','\147',
          '\150','\151','\152','\153','\154','\155','\156','\157',
          '\160','\161','\162','\163','\164','\165','\166','\167',
          '\170','\171','\172','\173','\174','\175','\176','\177' };
    
    private static final char[] uppercases = {
        '\000','\001','\002','\003','\004','\005','\006','\007',
        '\010','\011','\012','\013','\014','\015','\016','\017',
        '\020','\021','\022','\023','\024','\025','\026','\027',
        '\030','\031','\032','\033','\034','\035','\036','\037',
        '\040','\041','\042','\043','\044','\045','\046','\047',
        '\050','\051','\052','\053','\054','\055','\056','\057',
        '\060','\061','\062','\063','\064','\065','\066','\067',
        '\070','\071','\072','\073','\074','\075','\076','\077',
        '\100','\101','\102','\103','\104','\105','\106','\107',
        '\110','\111','\112','\113','\114','\115','\116','\117',
        '\120','\121','\122','\123','\124','\125','\126','\127',
        '\130','\131','\132','\133','\134','\135','\136','\137',
        '\140','\101','\102','\103','\104','\105','\106','\107',
        '\110','\111','\112','\113','\114','\115','\116','\117',
        '\120','\121','\122','\123','\124','\125','\126','\127',
        '\130','\131','\132','\173','\174','\175','\176','\177' };

    /* ------------------------------------------------------------ */
    
    
    /**
     * This method performance is about java.lang.String.toLowerCase 4 times.
     * 
     * WARNING: Only works on ascii (not unicode)
     * 
     * 经过测试，性能大约是 java.lang.String.toLowerCase 的4倍。
     * 
     * @param s 
     * @return
     */
    public static String asciiToLowerCase(String s)
    {
        char[] c = s.toCharArray();
        int i = s.length();

        // look for first conversion
        while ( i-- > 0 ){
            char c1 = c[i];
            if (c1 <= 127){
                char c2 = lowercases[c1];
                if ( c1 != c2 ) {
                    c[i] = c2;
                    break;
                }
            }
        }
        
        if( i == 0 ){
            return s;
        }
        
        while ( i-- > 0 ){
            if( c[i] <= 127 ){
                c[i] = lowercases[c[i]];
            }
        }
        
        return new String(c);
    }


    /**
     * This method performance is about java.lang.String.toUpperCase 4 times.
     * 
     * WARNING: Only works on ascii (not unicode)
     * 
     * 经过测试，性能大约是 java.lang.String.toUpperCase 的4倍。
     * 
     * @param s 
     * @return
     */
    public static String asciiToUpperCase(String s)
    {
        char[] c = s.toCharArray();
        int i = s.length();

        // look for first conversion
        while ( i-- > 0 ){
            char c1 = c[i];
            if (c1 <= 127){
                char c2 = uppercases[c1];
                if ( c1 != c2 ) {
                    c[i] = c2;
                    break;
                }
            }
        }
        
        if( i == 0 ){
            return s;
        }
        
        while ( i-- > 0 ){
            if( c[i] <= 127 ){
                c[i] = uppercases[c[i]];
            }
        }
        
        return new String(c);
    }
    
    
    
}