file_task

file_task_.idea_misc.xml

<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" default="true" project-jdk-name="1.8" project-jdk-type="JavaSDK">
    <output url="file://$PROJECT_DIR$/out" />
  </component>
</project>

file_task_.idea_modules.xml

<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
  <component name="ProjectModuleManager">
    <modules>
      <module fileurl="file://$PROJECT_DIR$/file_task.iml" filepath="$PROJECT_DIR$/file_task.iml" />
    </modules>
  </component>
</project>

file_task_file_task.iml

<?xml version="1.0" encoding="UTF-8"?>
<module type="JAVA_MODULE" version="4">
  <component name="NewModuleRootManager" inherit-compiler-output="true">
    <exclude-output />
    <content url="file://$MODULE_DIR$">
      <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
    </content>
    <orderEntry type="inheritedJdk" />
    <orderEntry type="sourceFolder" forTests="false" />
  </component>
</module>

file_task_src_FileClient.java

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;

public class FileClient {

    private static String directoryName;
    private static String fileName;
    private static File file = null;

    public static void main(String[] args) {

        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        try {
            System.out.println("enter the name of the file: ");
            fileName = reader.readLine();
            System.out.println("enter the name of the root directory: ");
            directoryName = reader.readLine();
        } catch (IOException exception) {
            exception.printStackTrace();
        }

        Thread thread = new Thread(new FileFounder(fileName, directoryName));
        thread.start();

        try {
            thread.join();
        } catch (InterruptedException exception) {
            exception.printStackTrace();
        }

        if (file != null) {
            System.out.println("\nfile " + fileName + " has been found, the full path: " + file.getAbsolutePath());
        } else {
            System.out.println("\nfile " + fileName + " has not been found in all subdirectories of " + directoryName);
        }
    }

    public static File getFile() {
        return file;
    }

    public static void setFile(File file) {
        FileClient.file = file;
    }
}

file_task_src_FileFounder.java

import java.io.File;
import java.io.FilenameFilter;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Arrays;

public class FileFounder implements Runnable {

    private String fileName;
    private String directoryName;

    public FileFounder(String fileName, String directoryName) {
        this.fileName = fileName;
        this.directoryName = directoryName;
    }

    @Override
    public void run() {

        if (FileClient.getFile() != null)
            return;

        if (Files.isDirectory(Paths.get(directoryName))) {
            System.out.println("directory " + directoryName + " exists");

            File file = new File(directoryName.concat("\\" + fileName));
            if(file.exists() && !file.isDirectory()) {
                FileClient.setFile(file);
                return;
            }

            File directory = new File(directoryName);
            String[] subDirectories = directory.list(new FilenameFilter() {
                @Override
                public boolean accept(File current, String name) {
                    return new File(current, name).isDirectory();
                }
            });

            if (subDirectories.length > 0) {
                System.out.println("subdirectories for " + directoryName + ": " + Arrays.toString(subDirectories));

                String[] subDirectoriesNames = new String[subDirectories.length];
                for (int i = 0; i < subDirectoriesNames.length; i++) {
                    subDirectoriesNames[i] = directoryName.concat("\\" + subDirectories[i]);
                }

                ArrayList<Thread> subDirectoriesThreads = new ArrayList<>(subDirectoriesNames.length);
                for (String subDirectoryName : subDirectoriesNames) {
                    Thread thread = new Thread(new FileFounder(fileName, subDirectoryName));
                    subDirectoriesThreads.add(thread);
                    thread.start();
                }

                try {
                    for (Thread thread : subDirectoriesThreads)
                        thread.join();
                } catch (InterruptedException exception) {
                    exception.printStackTrace();
                }

            } else {
                System.out.println("there's no subdirectories in the directory " + directoryName);
            }

        } else {
            System.out.println("directory " + directoryName + " doesn't exist");
        }
    }
}