IO (потоки ввода - вывода)

CopyFiles.java

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

/**
 *
 * @author kamaz
 */
public class CopyFiles {
    
    public static void copyFile (File in, File out) throws IOException {
        byte[] buffer = new byte[1024 * 1024];
        int readByte = 0;
        try (FileInputStream fis = new FileInputStream(in);
                FileOutputStream fos = new FileOutputStream(out)) {
            for (; (readByte = fis.read(buffer)) > 0;) {
                fos.write(buffer, 0, readByte);
            }
        } catch (IOException e) {
            throw e;
        }
    }
    
}

Main.java

import java.io.File;
import java.io.IOException;

/**
 *
 * @author kamaz
 */
public class Main {

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

        MyFileFilter mf = new MyFileFilter("doc", "docx");
        File folderOne = new File("E://Документація");

        File folderTwo = new File("Files");

        MyFileFilter.createFile(folderOne, folderTwo, mf);
    }

}

MyFileFilter.java

import java.io.File;
import java.io.FileFilter;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

/**
 *
 * @author kamaz
 */
public class MyFileFilter implements FileFilter {

    private String[] arr;

    public MyFileFilter(String... arr) {
        super();
        this.arr = arr;
    }

    private boolean check(String text) {
        for (String stringExt : arr) {
            if (stringExt.equals(text)) {
                return true;
            }
        }
        return false;
    }

    @Override
    public boolean accept(File pathname) {
        int pointerIndex = pathname.getName().lastIndexOf(".");
        if (pointerIndex == -1) {
            return false;
        }
        String text = pathname.getName().substring(pointerIndex + 1);
        return check(text);
    }
    
    public static void createFile(File folderOne, File folderTwo, MyFileFilter mf) throws IOException {
        folderTwo.mkdirs();
        
        File[] fileList = folderOne.listFiles(mf);
        
        for (File fileIn : fileList) {
        File outOne = new File(folderTwo.getName() + "/" + fileIn.getName());
        outOne.createNewFile();
        CopyFiles.copyFile(fileIn, outOne);
        }
    }

}