我有一个方法可以返回String[]当前路径Files的名称，我正在尝试做的是制作一个返回给我的方法String[]名称，但按日期排序，按大小排序，我差不多完成了这个，但我遗漏了一些东西。我知道要对它进行排序Arrays.sort()，但问题是我不知道如何加入所有。
这就是我所拥有的（没有排序）
File dir = new File(this.path);
File[] filelist = dir.listFiles();
String[] theNamesOfFiles;
if (filelist.length == 0) {
theNamesOfFiles = new String[1];
} else {
theNamesOfFiles = new String[filelist.length];
}
if (filelist.length == 0) {
theNamesOfFiles[0] = "This folder is empty";
} else {
for (int i = 0; i < theNamesOfFiles.length; i++) {
theNamesOfFiles[i] = filelist[i].getName();
}
}
return theNamesOfFiles;
现在我尝试使用SortByDate()方法，但我不知道如何让那些File[]制作上一个方法：
public File[] SortByDate(File test) {
final File[] sortedByDate = test.listFiles();
if (sortedByDate != null && sortedByDate.length > 1) {
Arrays.sort(sortedByDate, new Comparator < File > () {
@Override
public int compare(File object1, File object2) {
return (int)((object1.lastModified() > object2.lastModified()) ? object1.lastModified() : object2.lastModified());
}
});
return sortedByDate;
}
return sortedByDate;
}
我想我知道如何获得File的大小：
Integer.parseInt(String.valueOf(filelist[i].length() / 1024))
我还应该使用Compare<File>()吗？
我误解或遗失的是什么？
现在我尝试创建一个private File[] SortedByDate;，我已经实现了这个方法：
public void SortByDate() {
File test = new File(this.path);
this.SortedByDate = test.listFiles();
if (this.SortedByDate != null && this.SortedByDate.length > 1) {
Arrays.sort(this.SortedByDate, new Comparator < File > () {
@Override
public int compare(File object1, File object2) {
return (int)((object1.lastModified() > object2.lastModified()) ? object1.lastModified() : object2.lastModified());
}
});
}
for (int i = 0; i < this.SortedByDate.length; i++) {
Log.d("SortedByDate", this.SortedByDate[i].getName());
}
}
然后我创建了另一种看起来像的方法：
public String[] FilesFoundSortedByDate() {
SortByDate();
String[] theNamesOfFiles;
if (this.SortedByDate.length == 0) {
theNamesOfFiles = new String[1];
} else {
theNamesOfFiles = new String[this.SortedByDate.length];
}
if (this.SortedByDate.length == 0) {
theNamesOfFiles[0] = "This folder is empty";
} else {
for (int i = 0; i < theNamesOfFiles.length; i++) {
theNamesOfFiles[i] = this.SortedByDate[i].getName();
}
}
return theNamesOfFiles;
}
我想调用SortByDate的函数，然后使用创建的新属性的File []，但它没有排序。
答案 0 :(得分：3)
排序功能。根据需要修改它们。他们所做的只是使用值和compareTo()方法调用。理解这一点的关键是here。
根据需要将字符串逻辑组合在一起，形成您的排序函数，因为它实际的排序要求有点令人困惑。
private void sortByName(File[] files){
Arrays.sort(files, new Comparator<File>() {
@Override
public int compare(File t, File t1) {
return t.getName().compareTo(t1.getName());
}
});
}
private void sortByDate(File[] files){
Arrays.sort(files, new Comparator<File>() {
@Override
public int compare(File t, File t1) {
return (int) (t.lastModified() - t1.lastModified());
}
});
}
private void sortBySize(File[] files){
Arrays.sort(files, new Comparator<File>() {
@Override
public int compare(File t, File t1) {
return (int) (t.length() - t1.length());
}
});
}
答案 1 :(得分：1)
按日期升序和大小升序排序文件列表。
void SortByDateAndSize(File[] fileList) {
Arrays.sort(fileList, new Comparator<File>() {
@Override
public int compare(File o1, File o2) {
int r = Long.compare(o1.lastModified(), o2.lastModified());
if (r != 0)
return r;
return Long.compare(o1.length(), o2.length());
}
});
}
答案 2 :(得分：1)
我使用Java 8 Stream和Lamda功能来创建一个函数，该函数按上次修改时间和文件大小对目录中的文件进行排序。
public static String[] getSortedFileNames(File directory) {
return Arrays
// get all the files from the directory
.stream(directory.listFiles())
// sorting them first by last modified time and then by length
// the sorted function uses a comparator (like your Comparator<File>
// or a function which compares two files
.sorted((f1, f2) -> {
// first compare the two files by last modified (newest files first => compare f2 with f1)
final int compareModified = Long.compare(f2.lastModified(), f1.lastModified());
return compareModified != 0
? compareModified
: Long.compare(f2.length(), f1.length()); // the two files have the same last modified time,
// lets sort them by file size (biggest files first)
})
// get the name of the file
.map(File::getName)
// return the names from the sorted files in a String array
.toArray(String[]::new);
}
使用Files.list(path)更新（更新的方法现在可以抛出IOException）：
public static String[] sortFiles(File directory) throws IOException {
return Files
// get all the paths in the directory
.list(directory.toPath())
// turn paths into files
.map(Path::toFile)
// sortying them first by last modfied and then by length
.sorted((f1, f2) -> {
// the sorted function uses a comparotor or a function which compares two files
// first compare the two files by last modified (newest files first => * -1)
final int compareModified = Long.compare(f2.lastModified(), f1.lastModified());
return compareModified != 0
? compareModified
: Long.compare(f2.length(), f1.length()); // the two files have the same last modified time,
// lets sort them by file size (biggist first)
})
// get the name of the file
.map(File::getName)
// return the names from the sorted files in a String array
.toArray(String[]::new);
}
仅使用nio文件API更新2。
使用Path和Files.getLastModifiedTime比较Files.size。
当其中一个方法抛出RuntimeException时，我必须抛出IOException，因为它是not possible to throw a (checked) exception from a lambda in a stream（在compare的{{1}}方法中也是不可能的}}）。
Comparator<Path>答案 3 :(得分：1)
我把一个带有lambdas的小演示文件放在一起
public static void main(String[] args) {
File f = new File(System.getProperty("user.home") + "/temp");
List<File> files = Arrays.asList(f.listFiles(((dir, name) -> !(new File(dir,name)).isDirectory())));
System.out.println("****** Listing as received *********** ");
files.forEach(file -> System.out.println(file.getName()));
System.out.println("****** Listing sorted by length *********** ");
files.sort((f1,f2) -> Long.compare(f1.length(),f2.length()));
files.forEach(file -> System.out.println(
String.format("%-30s length = %2d",file.getName(),file.length())));
System.out.println("****** Listing sorted by date **************");
files.sort((f1,f2) -> Long.compare(f1.lastModified(),f2.lastModified()));
files.stream()
.map(file -> String.format("%-30s date mod = %2$td-%2tm-%2$tY %2$tH:%2$tM:%2$ts",file.getName(), new Date(file.lastModified())))
.collect(Collectors.toList()).forEach(System.out::println);
}
生成的输出
****** Listing as received *********** .DS_Store allclasses-frame.html allclasses-noframe.html alltext_awesome.test alltext_java8.test alltext_oldjava.text bigDbTesting.mv.db bigDbTesting.trace.db constant-values.html cx_d_entity_npn.txt default-centos-66-pmd1.box deprecated-list.html F_TXN_Refresh.SFS.kjb fakedata.mv.db faker.mv.db help-doc.html index.html jdk160_26.zip keepPass_v0.xml ldapinfo.txt overview-frame.html overview-summary.html overview-tree.html package-list script.js simpleDbToFileTest.txt simpleDbToFileTest2.txt stringIncrementer.jar stylesheet.css table.csv temp.sql those.enc.copy.properties those.enc.properties those.properties untitled text 4.txt untitled text.txt untitled text111.txt ****** Listing sorted by length *********** cx_d_entity_npn.txt length = 0 package-list length = 20 untitled text 4.txt length = 39 untitled text111.txt length = 132 simpleDbToFileTest.txt length = 180 ldapinfo.txt length = 295 untitled text.txt length = 695 script.js length = 827 overview-frame.html length = 850 those.enc.copy.properties length = 853 those.enc.properties length = 853 allclasses-noframe.html length = 1243 allclasses-frame.html length = 1343 temp.sql length = 1504 those.properties length = 1836 bigDbTesting.trace.db length = 2673 index.html length = 2863 simpleDbToFileTest2.txt length = 3201 deprecated-list.html length = 3514 constant-values.html length = 3564 overview-summary.html length = 4043 alltext_awesome.test length = 4546 alltext_java8.test length = 4546 alltext_oldjava.text length = 4546 overview-tree.html length = 4821 F_TXN_Refresh.SFS.kjb length = 7254 help-doc.html length = 8242 stringIncrementer.jar length = 12243 .DS_Store length = 12292 stylesheet.css length = 12808 keepPass_v0.xml length = 14810 faker.mv.db length = 28672 table.csv length = 47820 bigDbTesting.mv.db length = 212992 fakedata.mv.db length = 75051008 jdk160_26.zip length = 87253361 default-centos-66-pmd1.box length = 20131307999 ****** Listing sorted by date ************** jdk160_26.zip date mod = 04-04-2014 10:09:1396620572 simpleDbToFileTest2.txt date mod = 02-07-2014 14:07:1404324435 simpleDbToFileTest.txt date mod = 03-07-2014 08:05:1404389127 cx_d_entity_npn.txt date mod = 23-09-2014 15:39:1411501165 F_TXN_Refresh.SFS.kjb date mod = 23-09-2014 16:17:1411503474 keepPass_v0.xml date mod = 21-10-2014 16:48:1413924527 ldapinfo.txt date mod = 22-10-2014 10:39:1413988799 untitled text111.txt date mod = 08-12-2014 09:05:1418047503 default-centos-66-pmd1.box date mod = 03-02-2015 10:56:1422978975 untitled text 4.txt date mod = 06-02-2015 23:14:1423282475 untitled text.txt date mod = 06-02-2015 23:14:1423282475 stringIncrementer.jar date mod = 13-02-2015 18:19:1423869592 fakedata.mv.db date mod = 19-02-2015 08:31:1424352716 faker.mv.db date mod = 24-03-2015 14:49:1427222991 table.csv date mod = 30-04-2015 10:07:1430402823 bigDbTesting.mv.db date mod = 30-04-2015 10:33:1430404409 bigDbTesting.trace.db date mod = 30-04-2015 10:43:1430405015 .DS_Store date mod = 27-05-2015 09:28:1432733304 alltext_awesome.test date mod = 08-06-2015 08:51:1433767887 alltext_java8.test date mod = 08-06-2015 08:51:1433767887 alltext_oldjava.text date mod = 08-06-2015 08:51:1433767887 stylesheet.css date mod = 08-06-2015 10:24:1433773446 package-list date mod = 08-06-2015 10:25:1433773522 script.js date mod = 08-06-2015 10:25:1433773522 overview-frame.html date mod = 08-06-2015 10:25:1433773522 allclasses-noframe.html date mod = 08-06-2015 10:25:1433773522 allclasses-frame.html date mod = 08-06-2015 10:25:1433773522 index.html date mod = 08-06-2015 10:25:1433773522 deprecated-list.html date mod = 08-06-2015 10:25:1433773522 constant-values.html date mod = 08-06-2015 10:25:1433773522 overview-summary.html date mod = 08-06-2015 10:25:1433773522 overview-tree.html date mod = 08-06-2015 10:25:1433773522 help-doc.html date mod = 08-06-2015 10:25:1433773522 temp.sql date mod = 08-06-2015 15:21:1433791297 those.properties date mod = 11-06-2015 14:33:1434047622 those.enc.copy.properties date mod = 11-06-2015 15:38:1434051531 those.enc.properties date mod = 11-06-2015 15:49:1434052178
答案 4 :(得分：1)
最简单的方法是：
File directory = new File(".");
File[] files = directory.listFiles((FileFilter) FileFileFilter.FILE);
Arrays.sort(files, LastModifiedFileComparator.LASTMODIFIED_COMPARATOR);
Arrays.sort(files, LastModifiedFileComparator.LASTMODIFIED_REVERSE);
然后
FLAG_LAYOUT_IN_SCREEN该库中的其他比较器：
CompositeFileComparator， DefaultFileComparator， DirectoryFileComparator， ExtensionFileComparator， NameFileComparator， PathFileComparator， SizeFileComparator。
答案 5 :(得分：0)
即使这篇文章已经有一个绝对正确的答案，我试图在没有旧的Java IO Package的情况下做所有事情，只使用NIO功能来解决性能问题。所以这里（降序排序）。我不知道它是否在Android中可用，但在Java 8中它是。 （基于Peter Neyens解决方案的内容）。此解决方案基于我Why does the java DirectoryStream perform so slow?
中的其他问题import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
public class FileSorter2 {
public String[] getSortedFileList(Path dir) throws IOException {
return Files.list(dir).map(PathInfo::new).sorted().map(p -> p.
getFileName()).toArray(String[]::new);
}
public static void main(String[] args) throws IOException {
// some testing, this main throws IOException
Path dir = Paths.get("C:\\Windows\\system32");
FileSorter2 fs = new FileSorter2();
long before = System.currentTimeMillis();
String[] sortedFileNames = fs.getSortedFileList(dir);
long after = System.currentTimeMillis();
System.out.println("Time needed: " + (after - before));
}
// Helping class to cache object which is compared
static class PathInfo implements Comparable<PathInfo> {
private final String fileName;
private final long modified;
private final long size;
public PathInfo(Path path) {
try {
fileName = path.getFileName().toString();
modified = Files.getLastModifiedTime(path).toMillis();
size = Files.size(path);
} catch (IOException ex) {
throw new UncheckedIOException(ex);
}
}
@Override
public int compareTo(PathInfo o) {
int cmp = Long.compare(modified, o.modified);
if (cmp == 0) {
cmp = Long.compare(size, o.size);
}
return cmp;
}
public String getFileName() {
return fileName;
}
}
}