blocks|key|1436973|text|如果我没记错，Arrays.sort(...)获取将用于进行排序的Comparator<>。您可以提供它的一个实现来查看字符串的扩展部分。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1436974|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

If I remember correctly, the Arrays.sort(...) takes a Comparator&lt;> that it will use to do the sorting. You can provide an implementation of it that looks at the extension part of the string.

blocks|key|1437025|text|您可以实现字符串的自定义Comparator。使其按照'.'的最后一个索引之后的子字符串对它们进行排序。然后将比较器和数组传入|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1437026|Arrays.sort(stringArray,+yourComparator);

//++An+implementation+of+the+compare+method
public+int+compare(String+o1,+String+o2)+{
++++return+o1.substring(o1.lastIndexOf('.')).compareTo(o2.substring(o2.lastIndexOf('.'));
}|code-block|syntax|javascript|1437027|entityMap|0|LINK|mutability|MUTABLE|url|http://java.sun.com/javase/6/docs/api/java/util/Comparator.html^0|R|3|C|A|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@$9|V|A|W|1|X]]|E|$]]|$1|F|3|G|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

You can implement a custom <a href="http://java.sun.com/javase/6/docs/api/java/util/Comparator.html" rel="nofollow noreferrer">Comparator</a> of Strings. Make it sort them by the substring after the last index of <code>'.'</code>. Then pass in the comparator and your array into 

<pre><code>Arrays.sort(stringArray, yourComparator);

// An implementation of the compare method
public int compare(String o1, String o2) {
 return o1.substring(o1.lastIndexOf('.')).compareTo(o2.substring(o2.lastIndexOf('.'));
}
</code></pre>

blocks|key|1437093|text|创建一个比较器并比较字符串扩展名。看一下下面的内容|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1437094|http://java.sun.com/j2se/1.4.2/docs/api/java/util/Comparator.html|offset|length|1437095|然后将您的字符串列表传递给Arrays.sort(列表，比较器)|1437096|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|1T|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@$D|Q|E|R|1|S]]|A|$]]|$1|F|3|G|5|6|7|T|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|U|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|C]]]]

Create a Comparator and compare the string extensions. Take a look at the following

<a href="http://java.sun.com/j2se/1.4.2/docs/api/java/util/Comparator.html" rel="nofollow noreferrer">http://java.sun.com/j2se/1.4.2/docs/api/java/util/Comparator.html</a>

Then pass in your List of strings to Arrays.sort(List, Comparator)

blocks|key|1437134|text|创建您自己的Comparator，它将字符串视为文件名，并根据扩展名对它们进行比较。然后将Arrays.sort与比较器参数一起使用。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1437135|entityMap|0|LINK|mutability|MUTABLE|url|http://java.sun.com/j2se/1.4.2/docs/api/java/util/Comparator.html|1|http://java.sun.com/j2se/1.4.2/docs/api/java/util/Arrays.html^0|6|A|0|19|B|1|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]|$A|R|B|S|1|T]]|C|$]]|$1|D|3|-4|5|6|7|U|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]|L|$5|G|H|I|C|$J|M]]]]

Create your own <a href="http://java.sun.com/j2se/1.4.2/docs/api/java/util/Comparator.html" rel="nofollow noreferrer">Comparator</a> that treats the strings as filenames and compares them based on the extensions. Then use <a href="http://java.sun.com/j2se/1.4.2/docs/api/java/util/Arrays.html" rel="nofollow noreferrer">Arrays.sort</a> with the Comparator argument.

blocks|key|1651713|text|Arrays.sort(filenames,+new+Comparator<String>()+{
++++@Override
++++public+int+compare(String+s1,+String+s2)+{
++++++++//+the+%2B1+is+to+avoid+including+the+'.'+in+the+extension+and+to+avoid+exceptions
++++++++//+EDIT:
++++++++//+We+first+need+to+make+sure+that+either+both+files+or+neither+file
++++++++//+has+an+extension+(otherwise+we'll+end+up+comparing+the+extension+of+one
++++++++//+to+the+start+of+the+other,+or+else+throwing+an+exception)
++++++++final+int+s1Dot+=+s1.lastIndexOf('.');
++++++++final+int+s2Dot+=+s2.lastIndexOf('.');
++++++++if+((s1Dot+==+-1)+==+(s2Dot+==+-1))+{+//+both+or+neither
++++++++++++s1+=+s1.substring(s1Dot+%2B+1);
++++++++++++s2+=+s2.substring(s2Dot+%2B+1);
++++++++++++return+s1.compareTo(s2);
++++++++}+else+if+(s1Dot+==+-1)+{+//+only+s2+has+an+extension,+so+s1+goes+first
++++++++++++return+-1;
++++++++}+else+{+//+only+s1+has+an+extension,+so+s1+goes+second
++++++++++++return+1;
++++++++}
++++}
});|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1651714|完整性方面：java.util.Arrays和java.util.Comparator。|unstyled|offset|length|style|CODE|1651715|entityMap|0|LINK|mutability|MUTABLE|url|http://java.sun.com/javase/6/docs/api/java/util/Arrays.html|1|http://java.sun.com/javase/6/docs/api/java/util/Comparator.html^0|0|6|G|N|K|6|G|0|N|K|1|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|V|8|@$G|W|H|X|I|J]|$G|Y|H|Z|I|J]]|9|@$G|10|H|11|1|12]|$G|13|H|14|1|15]]|A|$]]|$1|K|3|-4|5|F|7|16|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]|S|$5|N|O|P|A|$Q|T]]]]

<pre><code>Arrays.sort(filenames, new Comparator&lt;String&gt;() {
 @Override
 public int compare(String s1, String s2) {
 // the +1 is to avoid including the '.' in the extension and to avoid exceptions
 // EDIT:
 // We first need to make sure that either both files or neither file
 // has an extension (otherwise we'll end up comparing the extension of one
 // to the start of the other, or else throwing an exception)
 final int s1Dot = s1.lastIndexOf('.');
 final int s2Dot = s2.lastIndexOf('.');
 if ((s1Dot == -1) == (s2Dot == -1)) { // both or neither
 s1 = s1.substring(s1Dot + 1);
 s2 = s2.substring(s2Dot + 1);
 return s1.compareTo(s2);
 } else if (s1Dot == -1) { // only s2 has an extension, so s1 goes first
 return -1;
 } else { // only s1 has an extension, so s1 goes second
 return 1;
 }
 }
});
</code></pre>

For completeness: <a href="http://java.sun.com/javase/6/docs/api/java/util/Arrays.html" rel="noreferrer"><code>java.util.Arrays</code></a> and <a href="http://java.sun.com/javase/6/docs/api/java/util/Comparator.html" rel="noreferrer"><code>java.util.Comparator</code></a>.

blocks|key|1437246|text|如果您只想按文件的扩展名对文件进行分组，而不关心实际的字母顺序，则可以使用以下命令：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1437247|我认为当文件名没有“”时，你能做的最简单的事情也同样适用。就是把名字颠倒过来比较一下。|1437248|Arrays.sort(ary,+new+Comparator<String>()+{
++++@Override
++++public+int+compare(String+o1,+String+o2)+{
++++++++String+r1+=+new+StringBuffer(o1).reverse().toString();
++++++++String+r2+=+new+StringBuffer(o2).reverse().toString();
++++++++return+r1.compareTo(r2);
++++}
});|code-block|syntax|javascript|1437249|遗憾的是，java的字符串甚至没有反向()。|1437250|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

If you just want to group the files by their extension and do not care about the actual alphabetical order, you can use this:

I think the simplest thing you can do that also works when the filenname does not have a "." is to just reverse the names and compare them.

<pre><code>Arrays.sort(ary, new Comparator&lt;String&gt;() {
 @Override
 public int compare(String o1, String o2) {
 String r1 = new StringBuffer(o1).reverse().toString();
 String r2 = new StringBuffer(o2).reverse().toString();
 return r1.compareTo(r2);
 }
});
</code></pre>

Its a shame that java's string does not even have a reverse().

blocks|key|1651804|text|++++String+DELIMETER+=+File.separator+%2B+".";
++++List<String>+orginalList+=+new+CopyOnWriteArrayList<>(Arrays.asList(listOfFileNames));
++++Set<String>+setOfuniqueExtension+=+new+TreeSet<>();

++++for+(String+item+:+listOfFileNames)+{
++++++++if+(item.contains("."))+{
++++++++++++String[]+split+=+item.split(DELIMETER);
++++++++++++String+temp+=+"."+%2B+split[split.length+-+1];
++++++++++++setOfuniqueExtension.add(temp);
++++++++}
++++}

++++List<String>+finalListOfAllFiles+=+new+LinkedList<>();
++++setOfuniqueExtension.stream().forEach((s1)+->+{
++++++++for+(int+i+=+0;+i+<+orginalList.size();+i%2B%2B)+{
++++++++++++if+(orginalList.get(i).contains(s1))+{
++++++++++++++++finalListOfAllFiles.add(orginalList.get(i));
++++++++++++++++orginalList.remove(orginalList.get(i));
++++++++++++++++i--;
++++++++++++}
++++++++}
++++});

++++orginalList.stream().filter((s1)+->+(!finalListOfAllFiles.contains(s1))).forEach((s1)+->+{
++++++++finalListOfAllFiles.add(s1);
++++});

++++return+finalListOfAllFiles;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1651805|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code> String DELIMETER = File.separator + ".";
 List&lt;String&gt; orginalList = new CopyOnWriteArrayList&lt;&gt;(Arrays.asList(listOfFileNames));
 Set&lt;String&gt; setOfuniqueExtension = new TreeSet&lt;&gt;();

 for (String item : listOfFileNames) {
 if (item.contains(".")) {
 String[] split = item.split(DELIMETER);
 String temp = "." + split[split.length - 1];
 setOfuniqueExtension.add(temp);
 }
 }

 List&lt;String&gt; finalListOfAllFiles = new LinkedList&lt;&gt;();
 setOfuniqueExtension.stream().forEach((s1) -&gt; {
 for (int i = 0; i &lt; orginalList.size(); i++) {
 if (orginalList.get(i).contains(s1)) {
 finalListOfAllFiles.add(orginalList.get(i));
 orginalList.remove(orginalList.get(i));
 i--;
 }
 }
 });

 orginalList.stream().filter((s1) -&gt; (!finalListOfAllFiles.contains(s1))).forEach((s1) -&gt; {
 finalListOfAllFiles.add(s1);
 });

 return finalListOfAllFiles;
</code></pre>

I have an array of filenames and need to sort that array by the extensions of the filename. Is there an easy way to do this?

Java sort String array of file names by their extension

我有一个文件名数组，需要根据文件名的扩展名对该数组进行排序。有什么简单的方法可以做到这一点吗？

问Java排序按扩展名排列的文件名字符串数组
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