CopyApp.java

import java.io.File;
import java.util.ArrayList;
import java.util.List;

public class CopyApp {

	public void copyFiles(String from, String to) {
		List<File> files = listFile(from);

		List<Thread> threads = new ArrayList<>();
		for (File file : files) {
			String name = file.getName();
			String copyTo = to + File.separator + name;

			CopyThread copyThread = new CopyThread(file.getAbsolutePath(), copyTo);
			copyThread.start();

			threads.add(copyThread);
		}

		for (Thread thread : threads) {
			try {
				thread.join();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}

		System.out.println("Copy complete");
	}

	private List<File> listFile(String from) {
		File sourceFile = new File(from);
		List<File> files = new ArrayList<>();

		if (sourceFile.isFile()) {
			files.add(sourceFile);
		} else {
			try {
				listFile(sourceFile, files);
			} catch (Exception e) {
				e.printStackTrace();
			}
		}

		return files;
	}

	private void listFile(File file, List<File> lists) {

		if (file.isDirectory()) {
			for (File f : file.listFiles()) {
				listFile(f, lists);
			}
		} else {
			lists.add(file);
		}
	}

	public static void main(String[] args) {
		if (args.length < 2) {
			usage();
		}

		String source = args[0];
		String destination = args[1];

		CopyApp copyApp = new CopyApp();
		copyApp.copyFiles(source, destination);
	}

	static void usage() {
		System.err.println("java CopyApp source target-dir");
		System.err.println("java CopyApp source-dir target-dir");
		System.exit(-1);
	}

}