arraylist - How to implement recursive all possible combination of any set (JAVA) -

can give me few clues or writing combination function output possible combination of set. have idea. find hard.

something in java.

string set[] = {"java","c++","python"};  arraylist<string> list = new arraylist<string>();  public void combination(string[] set) {      if (set.length == 0) {         nothing      } else if (this combination set) {        add list     } } 

here's simple example of combinations of letters in string, give algorithm. see if can transfer algorithm example.

    public class stringlib {      public static void combine(string str){         int length=str.length();          stringbuffer output=new stringbuffer();          combination(str,length,output,0);     }      static void combination(string str, int length, stringbuffer output, int level){         /* show arms-length recursion style better peformance */         if (level==length)             return;         else{             for(int i=level;i<length;i++){                 output.append(str.charat(i));                 system.out.println(output.tostring());                 combination(str,length,output,i+1);                 output.deletecharat(output.length()-1);             }         }     }       public static void main(string[] args){         combine("abc");     } }  /*output:  ab abc ac b bc c */ 

just in case need permutations:

import java.util.*;  public class permutations {   public static void main(string[] args)   {     string str = new string("abc");     stringbuffer output = new stringbuffer();      boolean used[] = {false, false, false};      permute.printpermutations(0, output, used, str);   } }   public class permute{    static void printpermutations(int level, stringbuffer output, boolean used[], string orig){       int len = orig.length();       if (level == len){           system.out.println(output);       }       else{           (int = 0; < len; i++){                   //recurse if not used               if (!used[i]){                   output.append(orig.charat(i));                   used[i] = true;                   printpermutations(level+1, output, used, orig);                   output.deletecharat(output.length() - 1);                   used[i] = false;               }           }       }   } }     /*output:  abc acb bac bca cab cba  */