递归生成小于某个数的所有集合

package com;

public class ConpectOne
{
public static void main(String[] args)
{
ConpectOne co = new ConpectOne();
String J = "";
int y = 0;
co.conceptOne(J, y);
}
public void conceptOne(String J,int y)
{
int n = 5;
String K = new String();
for(int j = y; j < n; j ++)
{
K = J + j;
System.out.println(K);
conceptOne(K,j + 1);
}
}
}