import org.junit.Test;public class AllSort { public void permutation(char[] buf, int start, int end) {  if (start == end) {// 當只要求對數組中一個字母進行全排列時，只要就按該數組輸出即可   for (int i = 0; i <= end; i++) {    System.out.print(buf[i]);   }   System.out.println();  } else {// 多個字母全排列   for (int i = start; i <= end; i++) {    char temp = buf[start];// 交換數組第一個元素與后續的元素    buf[start] = buf[i];    buf[i] = temp;    permutation(buf, start + 1, end);// 后續元素遞歸全排列    temp = buf[start];// 將交換后的數組還原    buf[start] = buf[i];    buf[i] = temp;   }  } } @Test public void testPermutation() throws Exception {  char[] buf = new char[] { 'a', 'b', 'c' };  permutation(buf, 0, 2); } }