Java 嵌入式比较器类

Question

我在编译我编写的一些代码时遇到了问题。该代码旨在对目录数组进行排序，然后返回排序后的数组。传入程序的数组如下所示：{"/","/usr/","/usr/local/","/usr/local/bin/","/games/","/games/snake/","/homework/","/temp/downloads/"}

对此的排序答案是：

{ "/", "/games/", "/homework/", "/usr/", "/games/snake/", 
     "/temp/downloads/", "/usr/local/", "/usr/local/bin/" }

所以基本上，最浅的目录放在最前面。如果两个目录具有相同的深度，我们根据第一个单词按字母顺序排序。 到目前为止，我的代码是这样的：

import java.util.Arrays;
import java.util.Comparator;

public class Dirsort {

  class APTComp implements Comparator<String> {

      public int compare(String a, String b) {
          String[] d1 = a.split("/");
          String[] d2 = b.split("/");
          int diff = d1.length - d2.length;

          if (diff != 0) {
            return diff;
          } //{"/","/usr/","/usr/local/","/usr/local/bin/","/games/","/games/snake/","/homework/","/temp/downloads/"}

          return a.compareTo(b);
        }



      public String[] sort(String[] dirs) {
        Arrays.sort(dirs);
        return dirs;
      }
}

你们能告诉我你们在这里发现了什么问题吗？我的 Arrays.sort() 调用是否使用了我的修改比较方法？

非常感谢， 朱奈德

Answer 1

Arrays.sort 不会直接按您的比较器排序，除非您调用。你应该使用

Arrays.sort(dirs, new APTComp());

修改后的代码：

import java.util.Arrays;
import java.util.Comparator;

public class Main {

  class APTComp implements Comparator<String> {

      public int compare(String a, String b) {
          String[] d1 = a.split("/");
          String[] d2 = b.split("/");
          int diff = d1.length - d2.length;

          if (diff != 0) {
            return diff;
          } //{"/","/usr/","/usr/local/","/usr/local/bin/","/games/","/games/snake/","/homework/","/temp/downloads/"}

          return a.compareTo(b);
        }
  }


      public String[] sort(String[] dirs) {
        Arrays.sort(dirs, new APTComp());
        return dirs;
      }

      public static void main(String[] args) {
          Main main = new Main();
          String[] result = main.sort(new String[] {"/","/usr/","/usr/local/","/usr/local/bin/","/games/","/games/snake/","/homework/","/temp/downloads/"});
          for(int i=0; i<result.length; i++) {
            System.out.println(i + ": " + result[i]);
          }
      }
}

结果： 0：/ 1：/游戏/ 2：/作业/ 3：/usr/ 4：/游戏/蛇/ 5：/临时/下载/ 6：/usr/本地/ 7：/usr/local/bin/

见another example

Answer 2

此代码有效，请检查

import java.util.Arrays;
import java.util.Comparator;

public class Dirsort {

class APTComp implements Comparator<String> {

    public int compare(String a, String b) {
        String[] d1 = a.split("/");
        String[] d2 = b.split("/");
        int diff = d1.length - d2.length;
        if (diff != 0) {
            return diff;
        }
        return a.compareTo(b);
    }

    public String[] sort(String[] dirs) {
        Arrays.sort(dirs);
        return dirs;
    }
}

public static void main (String[] args) {
  String[] arr = new String[] {"/","/usr/","/usr/local/","/usr/local/bin/","/games/","/games/snake/","/homework/","/temp/downloads/"};
Dirsort ds = new Dirsort();
  Arrays.sort(arr, ds.new APTComp());
  for (String s : arr) {
      System.out.println(s);
  }
}
}

输出：
/
/游戏/
/家庭作业/
/usr/
/游戏/蛇/
/temp/下载/
/usr/local/
/usr/local/bin/

Answer 3

默认 Arrays.sort() 方法使用自然顺序进行排序。由于您的情况下的数组是字符串，默认情况下它将根据字符串的字母顺序进行排序。

要获得您想要的结果，您必须将自定义比较器实现的实例传递给 Arrays.sort()。

将APTComp 类中的public String[] sort(String[] dirs) 方法替换为：

public String[] sort(String[] dirs) 
{
    Arrays.sort(dirs, new APTComp());
    return dirs;
}