Java recursively searches for files

September 17, 2018

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Java directoryfrom (e.g. time, place, numerical quantity)recursiveSearch for files in

Java introduces a sample program that recursively searches for files in a specified directory, including subdirectories, and obtains a list of files that match the search criteria.
They are equivalent to the UNIX command ls -R or the Windows command dir /s.
You can also specify * as a wildcard character in the file name to be searched, or use a regular expression to search.

　As an example of usage, the following recursively searches the directory filelist, including subdirectories, to obtain a list of files with the extension java.

FileSearch search = new FileSearch();
File[] files = search.listFiles("C:/filelist/", "*.java");

sample program

import java.io.File; import java.text.SimpleDateFormat; import java.util.Date; import java.util.TreeSet; /** * */ public class FileSearch { public static final int TYPE_FILE_OR_DIR = 1; public static final int TYPE_FILE = 2; public static final int TYPE_DIR = 3; /** * From the specified directory [directoryPath], * Search the file [fileName] to be searched recursively and find the corresponding file. * Returns a list of file objects. * * example) * File[] files =listFiles(“C:/filelist/”, “*.java”); * The example above searches the directory filelist recursively and * Get a list of files with the extension java. * * @param directoryPath Path representing the directory to search * @param fileName File name to search for * You can specify * as a wildcard character in the file name. * @return File object matching the search */ public File[] listFiles(String directoryPath, String fileName) { // Convert * as wildcard character to regular expression if (fileName != null) { fileName = fileName.replace(“.”, “\\.”); fileName = fileName.replace(“*”, “.*”); } return listFiles(directoryPath, fileName, TYPE_FILE, true, 0); } /** * From the specified directory [directoryPath], specified as a regular expression * Search recursively for the file to be searched [fileNamePattern], * Returns a list of applicable file objects. * * You can also use the search condition to determine whether the file's update date has passed the specified number of days. * Can be specified. * * example) * File[] files = * listFiles(“C:/filelist/”, “*.java”,TYPE_FILE, true, 2); * In the above example, the directory filelist is searched recursively and updated less than 7 days ago. * Get a list of files with extension java. * * @param directoryPath Path representing the directory to search * @param fileNamePattern File name to search for [regular expression] * @param type The corresponding file object is specified by [type]. * The following can be specified * TYPE_FILE_OR_DIR・・・File and directory * TYPE_FILE・・・File * TYPE_DIR・・・Directory * @param isRecursive true to search recursively * @param period Search for files whose update date has passed the specified number of days. * Can be set whether or not * Not applicable if 0 * If 1 or more, search files after the specified number of days * If less than -1, search files older than the specified number of days * @return File object matching the search */ public File[] listFiles(String directoryPath, String fileNamePattern, int type, boolean isRecursive, int period) { File dir = new File(directoryPath); if (!dir.isDirectory()) { throw new IllegalArgumentException (“Path specified in argument[” + dir.getAbsolutePath() + “] is not a directory.”); } File[] files = dir.listFiles(); // its output for (int i = 0; i < files.length; i++) { File file = files[i]; addFile(type, fileNamePattern, set, file, period); // Search recursively and add to list recursively if it is a directory if (isRecursive && file.isDirectory()) { listFiles(file.getAbsolutePath(), fileNamePattern, type, isRecursive, period); } } return (File[]) set.toArray(new File[set.size()]); } private void addFile(int type, String match, TreeSet set, File file,int period) { switch (type) { case TYPE_FILE: if (!file.isFile()) { return; } break; case TYPE_DIR: if (!file.isDirectory()) { return; } break; } if (match != null && !file.getName().matches(match)) { return; } // If there is a specification whether the specified number of days have passed if (period != 0) { // File update date Date lastModifiedDate = new Date(file.lastModified()); String lastModifiedDateStr = new SimpleDateFormat(“yyyyMMdd”) .format(lastModifiedDate); // Specified date (calculated in milliseconds per day) long oneDayTime = 24L * 60L * 60L * 1000L; long periodTime = oneDayTime * Math.abs(period); Date designatedDate = new Date(System.currentTimeMillis() – periodTime); String designatedDateStr = new SimpleDateFormat(“yyyyMMdd”) .format(designatedDate); if (period > 0) { if (lastModifiedDateStr.compareTo(designatedDateStr) < 0) { return; } } else { if (lastModifiedDateStr.compareTo(designatedDateStr) > 0) { return; } } } // Store in list if all conditions are met set.add(file); } /** Use TreeSet to sort alphabetically. */ private TreeSet set = new TreeSet(); /** * If you want to continue using the instance after creating it, use this method. * Call must be cleared. * example) * FileSearch search = new FileSearch(); * File[] f1 = search.listFiles(C:/filelist/”, “*.java”); * search.clear(); * File[] f2 = search.listFiles(“C:/filelist/”, “*.jsp”); */ public void clear(){ set.clear(); } }

Execution Result

　To check the sample program, we created a filelist directory and prepared the following files.

The file name and update date are displayed.

The current date is2007/08/18Suppose it is.

C:\filelist
    │ aaa.java 2007/08/18
    │ bbb.java 2007/08/18
    └─dir
           ccc.java 2007/07/17
           ddd.java 2007/08/18
           eee.jpg 2007/08/16

◆Example of Execution
public static void main(String[] args) { String path = “C:\\filelist”; FileSearch search = new FileSearch(); System.out.println(“\n●Get all files”); File[] files = search.listFiles(path, null); printFileList(files); search.clear(); System.out.println(“\n●Get file with extension java”); files = search.listFiles(path, “*.java”); printFileList(files); search.clear(); System.out.println(“\n●Get all files and directories”); files = search.listFiles(path, null,search.TYPE_FILE_OR_DIR, true, 0); printFileList(files); search.clear(); System.out.println(“\n●Get files updated within 2 days from the current date”); files = search.listFiles(path, null,search.TYPE_FILE, true, 2); printFileList(files); search.clear(); System.out.println(“\n●Get old files older than 30 days from the current date”); files = search.listFiles(path, null,search.TYPE_FILE, true, -30); printFileList(files); search.clear(); } private static void printFileList(File[] files) { for (int i = 0; i < files.length; i++) { File file = files[i]; System.out.println((i + 1) + “: ” + file); } } 

◆Output result

Retrieve all files
1: C:\filelist\aaa.java
2: C:\filelist\bbb.java
3:C:\filelist\dir\ccc.java
4: C:\filelist\dir\ddd.java
5: C:\filelist\dir\dir\eee.jpg

Obtaining a file with the extension java
1: C:\filelist\aaa.java
2: C:\filelist\bbb.java
3: C:\filelist\dir\ccc.java
4: C:\filelist\dir\ddd.java

Get all files and directories
1: C:\filelist\aaa.java
2: C:\filelist\bbb.java
3: C:\filelist\dir
4: C:\filelist\dir\ccc.java
5: C:\filelist\dir\ddd.java
6: C:\filelist\dir\dir\eee.jpg

Obtaining files that have been updated since two days ago from the current date
1: C:\filelist\aaa.java
2: C:\filelist\bbb.java
3: C:\filelist\dir\ddd.java
4: C:\filelist\dir\dir\eee.jpg

Retrieve files older than 30 days from the current date
1: C:\filelist\dir\ccc.java

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