Java Files.find examples

By mkyong | Updated: December 2, 2020

Viewed: 14,525 (+81 pv/w)

Tags: file tree Files.find Files.walk find file java 8 java.io java.nio

The Files.find API is available since Java 8. It searches or finds files from a file tree quickly.

Topics

1. Files.find() method signature
2. Find files by filename
3. Find files by file size
4. Find files by last modified time

In the old days, we always use an error-prone recursive loop to walk a file tree. This Java 8 Files.find can save you a lot of time.

1. Files.find() Signature

Review the Files.find() signature.

public static Stream<Path> find(Path start,
                                int maxDepth,
                                BiPredicate<Path, BasicFileAttributes> matcher,
                                FileVisitOption... options)
        throws IOException

• The path, starting file or folder.
• The maxDepth defined the maximum number of directory levels to search. If we put 1, which means the search for top-level or root folder only, ignore all its subfolders; If we want to search for all folder levels, put Integer.MAX_VALUE.
• The BiPredicate<Path, BasicFileAttributes> is for condition checking or filtering.
• The FileVisitOption tells if we want to follow symbolic links, default is no. We can put FileVisitOption.FOLLOW_LINKS to follow symbolic links.

2. Find files by filename

This example uses Files.find() to find files that matched filename google.png, starting from the folder C:\\test, and included all levels of its subfolders.

package com.mkyong.io.api;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class FileFindExample1 {

    public static void main(String[] args) throws IOException {

        Path path = Paths.get("C:\\test");
        List<Path> result = findByFileName(path, "google.png");
        result.forEach(x -> System.out.println(x));

    }

    public static List<Path> findByFileName(Path path, String fileName)
            throws IOException {

        List<Path> result;
        try (Stream<Path> pathStream = Files.find(path,
                Integer.MAX_VALUE,
                (p, basicFileAttributes) ->
                        p.getFileName().toString().equalsIgnoreCase(fileName))
        ) {
            result = pathStream.collect(Collectors.toList());
        }
        return result;

    }

}

We also can use Files APIs to check the path further.

  try (Stream<Path> pathStream = Files.find(path,
         Integer.MAX_VALUE,
         (p, basicFileAttributes) ->{
             // if directory or no-read permission, ignore
             if(Files.isDirectory(p) || !Files.isReadable(p)){
                 return false;
             }
             return p.getFileName().toString().equalsIgnoreCase(fileName);
         })
 )

3. Find files by file size

This example uses Files.find() to find files containing file size greater or equals 100MB.

package com.mkyong.io.api;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class FileFindExample2 {

    public static void main(String[] args) throws IOException {

        Path path = Paths.get("C:\\Users\\mkyong\\Downloads");

        long fileSize = 1024 * 1024 * 100; // 100M

        List<Path> result = findByFileSize(path, fileSize);
        for (Path p : result) {
            System.out.println(String.format("%-40s [fileSize]: %,d", p, Files.size(p)));
        }

    }

    public static List<Path> findByFileSize(Path path, long fileSize)
            throws IOException {

        List<Path> result;
        try (Stream<Path> pathStream = Files.find(path,
                Integer.MAX_VALUE,
                (p, basicFileAttributes) -> {
                    try {
                        if (Files.isDirectory(p)) {   // ignore directory
                            return false;
                        }
                        return Files.size(p) >= fileSize;
                    } catch (IOException e) {
                        System.err.println("Unable to get the file size of path : " + path);
                    }
                    return false;
                }

        )) {
            result = pathStream.collect(Collectors.toList());
        }
        return result;

    }

}

Output samples.

C:\Users\mkyong\Downloads\hello.mp4 [fileSize]: 4,796,543,886
C:\Users\mkyong\Downloads\java.mp4.bk [fileSize]: 5,502,785,778
C:\Users\mkyong\Downloads\ubuntu-20.04.1-desktop-amd64.iso [fileSize]: 2,785,017,856

#...

4. Find files by last modified time

This example uses File.find() to find files containing last modified time equals or after yesterday.

package com.mkyong.io.api;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.BasicFileAttributes;
import java.nio.file.attribute.FileTime;
import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class FileFindExample3 {

    private static DateTimeFormatter DATE_FORMATTER
            = DateTimeFormatter.ofPattern("dd/MM/yyyy HH:mm:ss");

    public static void main(String[] args) throws IOException {

        // find files, LastModifiedTime from yesterday and above
        List<Path> result = findByLastModifiedTime(
                Paths.get("C:\\test"),
                Instant.now().minus(1, ChronoUnit.DAYS));

        for (Path p : result) {

            // formatting...
            BasicFileAttributes attrs = Files.readAttributes(p, BasicFileAttributes.class);
            FileTime time = attrs.lastModifiedTime();
            LocalDateTime localDateTime = time.toInstant()
                    .atZone(ZoneId.systemDefault())
                    .toLocalDateTime();

            System.out.println(String.format("%-40s [%s]", p, localDateTime.format(DATE_FORMATTER)));
        }

    }

    public static List<Path> findByLastModifiedTime(Path path, Instant instant)
            throws IOException {

        List<Path> result;
        try (Stream<Path> pathStream = Files.find(path,
                Integer.MAX_VALUE,
                (p, basicFileAttributes) -> {

                    if(Files.isDirectory(p) || !Files.isReadable(p)){
                        return false;
                    }

                    FileTime fileTime = basicFileAttributes.lastModifiedTime();
                    // negative if less, positive if greater
                    // 1 means fileTime equals or after the provided instant argument
                    // -1 means fileTime before the provided instant argument
                    int i = fileTime.toInstant().compareTo(instant);
                    return i > 0;
                }

        )) {
            result = pathStream.collect(Collectors.toList());
        }
        return result;

    }

}

Output samples and assume today is 02/12/2020

C:\test\a.txt                          [02/12/2020 13:01:20]
C:\test\b.txt                          [01/12/2020 12:11:21]

#...

Download Source Code

References

• Managing Metadata
• Files.find JavaDoc
• Files.walk examples
• Format FileTime in Java
• Java String Format Examples