Dmitry07

package my.com;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

public class Paths {
	public static void main(String[] args) {
		String str = "A1, A1\\BB1\\CCC1, A2\\BB1, A2\\BB1\\CCC1";
		ArrayList<String> paths = new ArrayList<String>(Arrays.asList(str.split(",")));

		System.out.println("======  Беган =======");
		System.out.println("Было");
		for(String i:paths){
			System.out.println(i);
		}
		
		Set<String> out = new TreeSet<String>(new Comparator<String>() {

			@Override
			public int compare(String o1, String o2) {
				return o2.compareTo(o1);
			}
			
		});
		for(String i : paths) {
			ArrayList<String> path = new ArrayList<String>(Arrays.asList(i.trim().split("\\\\")));
	
			for(int j = 1; j <= path.size(); j++) {
				List<String> s = path.subList(0, j);
				out.add(String.join("\\",s));
			}
		}

		System.out.println("=================");
		System.out.println("Сортировка туда");
		for(String i:out) {
			System.out.println(i);
		}

		System.out.println("=================");
		System.out.println("Сортировка обратно");
		Set<String> out1 = new TreeSet<String>();
		out1.addAll(out);
		for(String i:out1) {
			System.out.println(i);
		}
		System.out.println("======= Доне ======");
		
	}
}

======  Беган =======
Было
A1
 A1\BB1\CCC1
 A2\BB1
 A2\BB1\CCC1
=================
Сортировка туда
A2\BB1\CCC1
A2\BB1
A2
A1\BB1\CCC1
A1\BB1
A1
=================
Сортировка обратно
A1
A1\BB1
A1\BB1\CCC1
A2
A2\BB1
A2\BB1\CCC1
======= Доне ======