Java比较器字母数字字符串 [英] Java Comparator alphanumeric strings

问题描述

我想实现我的自定义比较器，以这种特殊方式对键映射进行排序:

I want to implement my custom Comparator to sort a map of keys in this particular way:

1
2
3
4
4a
4b
5
6
11
12
12a
...

我不知道该怎么做.我仅对数值实施了此操作:

And I dont know how can do it exactly. I have impelemented this only for numeric values:

aaa = new TreeMap<String, ArrayList<ETrack>>(
    new Comparator<String>()
    {
      @Override
      public int compare(String s1, String s2)
      {
        return Integer.valueOf(s1).compareTo(Integer.valueOf(s2));
      }
    });

但这并不是完整的解决方案.有什么主意吗?

But this is not obiouslly the complete solution. Any idea?

推荐答案

一种方法是将字符串映射到对象，并让这些对象实现 Comparable .

One approach is to map the strings to objects and let those objects implement Comparable.

您可以简化操作.如果您喜欢正则表达式，即使效率不高，也可以使用此技巧:

You can do it simpler. If you like regular expressions, you can use this trick, even though it is not too efficient:

// Make sure not to compile the pattern within the method, to spare us some time.
Pattern p = Pattern.compile("^([0-9]+)([a-z]?)$");

/**
 * Converts a string to a sortable integer, ensuring proper ordering:
 * "1" becomes 256
 * "1a" becomes 353
 * "1b" becomes 354
 * "2" becomes 512
 * "100" becomes 25600
 * "100a" becomes 25697
 */
int getSortOrder(String s) {
  Matcher m = p.matcher(s);
  if(!m.matches()) return 0;
  int major = Integer.parseInt(m.group(1));
  int minor = m.group(2).isEmpty() ? 0 : m.group(2).charAt(0);
  return (major << 8) | minor;
}

像这样使用它:

new Comparator<String>() {
  @Override
  public int compare(String s1, String s2) {
    return getSortOrder(s1) - getSortOrder(s2);
  }
}

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