JAva文字のすべての組合せ

package student_pro;

public class TestDemo {
		public static void main(String [] args) {
			String s="abc";
			fullPermutation(s);
		}
		private static void fullPermutation(String s) {
			permutation(s.toCharArray(),0,s.length()-1);
			
		}
		private static void permutation(char[] c, int start, int end) {
			if(start==end)
				System.out.println(new String(c));
			
			else {
				for(int i=start;i<=end;i++) {
					if(i!=start && c[i]!=c[start] || i==start) {  //     
						swap(c,i,start); 
						permutation(c,start+1,end);    //      
						swap(c,i,start);	
					}	
				}	
			}
			
		}
	 
		private static void swap(char[] c, int i, int start) {
			char temp=c[i];
			c[i]=c[start];
			c[start]=temp;
			
		}

}