Permutation of String - Iterative

Problem6

import java.util.ArrayList;

/**
 * all permutations of a string / char array
 * @author anupam
 */
public class Problem6 {
    public static ArrayList<String> allPerms(String str) {
        ArrayList<String> al = new ArrayList<>();
        int i=0;
        al.add(str);
        while(i < al.size()) {
            for(int j=0;j<al.get(i).length()-1;j++) {
                String temp = swap(al.get(i),j,j+1);
                if(exists(al,temp))
                    continue;
                else
                    al.add(temp);
            }
            i++;
        }
        return al;
    }
    
    private static String swap(String s, int i, int j) {
        char[] ch = s.toCharArray();
        char temp = ch[i];
        ch[i] = ch[j];
        ch[j] = temp;
        return new String(ch);
    }
    
    private static boolean exists(ArrayList<String> a, String s) {
        for(String a1 : a) {
            if(s.equals(a1))
                return true;            
        }
        return false;
    }
    
    public static void main(String[] args) {
        ArrayList<String> perms = allPerms("123");
        for(String s : perms) {
             System.out.println(s);             
        }
        System.out.println("Perm Count:"+perms.size());
    }
}