输出字符串的所有组合

public class Combine {    public static void printCom(String s ){        int len = s.length();        int com_count = 1<<len;        for (int i=1;i<com_count;i++){            for (int j=0;j<len;j++){                int k = i&(1<<j);                if (k!=0){                    System.out.print(s.charAt(j)+"");                }            }            System.out.println();        }    }    public static void main(String[] args) {        printCom("abc");    }}

ababcacbcabc