我认为这很容易找到预制的,但似乎我在网上找到的任何解决方案都只能解决部分问题。
我想对列表进行排序文件名(这些文件大多以人名和/或地址命名)由用户提供,有时使用不同的语言(主要是德语,到处混有一点法语和意大利语,很少有其他西方语言) 。
这个想法是以(德国)用户通常认为理智的方式排列的列表。这意味着顺序应该遵循Locale.GERMAN 的 java.text.Collator,但同时期望对字符串中的数字进行例外处理,因此“10”位于“2”之后。
我已经找到了在网络上进行自然排序的代码,但它依赖于逐个字符的比较(并且 Collator 不支持这一点)。我可以用子字符串来破解某些东西,但在比较器内,在每个比较调用上创建多个子字符串并不认为我是最明智的想法。
任何想法如何有效地实现这一点(在执行时间和执行时间),或者更好的是经过测试且随时可用的实现?
这是改编后的代码(基于Alphanum 算法 http://www.davekoelle.com/alphanum.html)如已接受的答案所示。该代码经过优化以减少垃圾产生并处理前导零 (01
import java.text.Collator;
import java.util.Comparator;
/**
* Comparator for ordering by Collator while treating digits numerically.
* This provides a "natural" order that humans usually perceive as 'logical'.
*
* It should work reasonably well for western languages (provided you
* use the proper collator when constructing). For free control over the
* Collator, use the constructor that takes a Collator as parameter.
* Configure the Collator using Collator.setDecomposition()/setStrength()
* to suit your requirements.
*/
public class AlphanumComparator implements Comparator<CharSequence> {
/**
* The collator used for comparison of the alpha part
*/
private final Collator collator;
/**
* Create comparator using platform default collator.
* (equivalent to using Collator.getInstance())
*/
public AlphanumComparator() {
this(Collator.getInstance());
}
/**
* Create comparator using specified collator
*/
public AlphanumComparator(final Collator collator) {
if (collator == null)
throw new IllegalArgumentException("collator must not be null");
this.collator = collator;
}
/**
* Ideally this would be generalized to Character.isDigit(), but I have
* no knowledge about arabic language and other digits, so I treat
* them as characters...
*/
private static boolean isDigit(final int character) {
// code between ASCII '0' and '9'?
return character >= 48 && character <= 57;
}
/**
* Get subsequence of only characters or only digits, but not mixed
*/
private static CharSequence getChunk(final CharSequence charSeq, final int start) {
int index = start;
final int length = charSeq.length();
final boolean mode = isDigit(charSeq.charAt(index++));
while (index < length) {
if (isDigit(charSeq.charAt(index)) != mode)
break;
++index;
}
return charSeq.subSequence(start, index);
}
/**
* Implements Comparator<CharSequence>.compare
*/
public int compare(final CharSequence charSeq1, final CharSequence charSeq2) {
final int length1 = charSeq1.length();
final int length2 = charSeq2.length();
int index1 = 0;
int index2 = 0;
int result = 0;
while (result == 0 && index1 < length1 && index2 < length2) {
final CharSequence chunk1 = getChunk(charSeq1, index1);
index1 += chunk1.length();
final CharSequence chunk2 = getChunk(charSeq2, index2);
index2 += chunk2.length();
if (isDigit(chunk1.charAt(0)) && isDigit(chunk2.charAt(0))) {
final int clen1 = chunk1.length();
final int clen2 = chunk2.length();
// count and skip leading zeros
int zeros1 = 0;
while (zeros1 < clen1 && chunk1.charAt(zeros1) == '0')
++zeros1;
// count and skip leading zeros
int zeros2 = 0;
while (zeros2 < clen2 && chunk2.charAt(zeros2) == '0')
++zeros2;
// the longer run of non-zero digits is greater
result = (clen1 - zeros1) - (clen2 - zeros2);
// if the length is the same, the first differing digit decides
// which one is deemed greater.
int subi1 = zeros1;
int subi2 = zeros2;
while (result == 0 && subi1 < clen1 && subi2 < clen2) {
result = chunk1.charAt(subi1++) - chunk2.charAt(subi2++);
}
// if still no difference, the longer zeros-prefix is greater
if (result == 0)
result = subi1 - subi2;
} else {
// in case we are working with Strings, toString() doesn't create
// any objects (String.toString() returns the same string itself).
result = collator.compare(chunk1.toString(), chunk2.toString());
}
}
// if there was no difference at all, let the longer one be the greater one
if (result == 0)
result = length1 - length2;
// limit result to (-1, 0, or 1)
return Integer.signum(result);
}
}
编辑2014-12-01:康斯坦丁彼得鲁赫诺夫在评论中指出的修复版本。
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