I want to revert these Lambda Expressions:
PathInfo::new
p -> p.getFileName()
While keeping the same performance discussed in the source. Here's the original method:
public List<String> getSortedFile(Path dir)
throws IOException
{
return Files.list(dir).map(PathInfo::new).sorted()
.map(p -> p.getFileName()).collect(Collectors.toList());
}
I'd like to revert them similar to how Javin Paul did it in this article:
// Before Java 8:
JButton show = new JButton("Show");
show.addActionListener(new ActionListener()
{
@Override
public void actionPerformed(ActionEvent e)
{
System.out.println("Event handling without lambda expression is boring");
}
});
// Java 8 way:
show.addActionListener((e) -> {
System.out.println("Light, Camera, Action !! Lambda expressions Rocks");
});
And here's the best solution discussed from the source:
import java.io.File;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.FileTime;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class FileSorter {
public List<String> getSortedFile(Path dir) throws IOException {
return Files.list(dir).map(PathInfo::new).sorted().map(p -> p.getFileName()).collect(Collectors.toList());
}
static class PathInfo implements Comparable<PathInfo> {
private final String fileName;
private final long modified;
private final long size;
public PathInfo(Path path) {
try {
// read the whole attributes once
BasicFileAttributes bfa = Files.readAttributes(path, BasicFileAttributes.class);
fileName = path.getFileName().toString();
modified = bfa.lastModifiedTime().toMillis();
size = bfa.size();
} 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;
}
}
public static void main(String[] args) throws IOException {
// File (io package)
File f = new File("C:\\Windows\\system32");
// Path (nio package)
Path dir = Paths.get("C:\\Windows\\system32");
FileSorter fs = new FileSorter();
long before4 = System.currentTimeMillis();
List<String> names4 = fs.getSortedFile(dir);
long after4 = System.currentTimeMillis();
System.out.println("Run time of Stream.sorted as List with caching: " + ((after4 - before4)));
}
}
