Java how to sort lowercase before uppercase strings

问题:

I want the files to be ordered by their abs path name, but I want the lowercase to be sorted before the uppercase. Example: Let's say I got 4 files:

files2.add("b"); files2.add("A"); files2.add("a"); files2.add("B"); 

the order with this code is: [A, B, a, b] I want it to be: [a, A, b, B]

import java.io.File; import java.util.*;  public class Abs {      public ArrayList<File> getOrder(ArrayList<File> files) {         Collections.sort(files, new Comparator<File>() {             public int compare(File file1, File file2) {                 return file1.getAbsolutePath().compareTo(file2.getAbsolutePath());             }         });         return files;     }  } 

回答1:

Check the Collator class.

You'll have to read carefully what those constants mean, but one of them should make it possible for you to put lowercase letters before the upper-case letters.

回答2:

You could implement your own Comparator, which in turn uses a Collator. See example.

回答3:

You can probably use library or utility classes with this behaviour, or you can build your own comparator.

    new Comparator<File>() {         public int compare(File file1, File file2) {             // Case-insensitive check             int comp = file1.getAbsolutePath().compareToIgnoreCase(file2.getAbsolutePath())             // If case-insensitive different, no need to check case             if(comp != 0) {                 return comp;             }             // Case-insensitive the same, check with case but inverse sign so upper-case comes after lower-case             return (-file1.getAbsolutePath().compareTo(file2.getAbsolutePath()));         }     } 

回答4:

As suggested by others, Collator does what you want. Writing one of those collator rules looked a bit scary, but it looks like the standard English Collator does exactly what you want:

public static void main(String... args) {     List<String> items = Arrays.asList("b", "A", "a", "B");     Collections.sort(items, Collator.getInstance(Locale.ENGLISH));     System.out.println(items); } 

gives:

[a, A, b, B] 

回答5:

Try this simple implementation :

public static void main(String[] args) {             List<String> list = new ArrayList<String>();             list.add("a");             list.add("b");             list.add("A");             list.add("B");             System.out.println(list);             Collections.sort(list, new Comparator<String>() {                     @Override                     public int compare(String o1, String o2) {                             if (o1.toLowerCase().equals(o2.toLowerCase())) {                                     if (o1.toLowerCase().equals(o1)) {                                             return -1;                                     } else {                                             return  1;                                     }                             } else {                                     return o1.toLowerCase().compareTo(o2.toLowerCase());                              }                     }             });             System.out.println(list);     } 

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