打印出ABCD四个字母的四位不相同组合

打印出ABCD四个字母的四位不相同组合，例如：ABCD、ACBD、ACDB...... 提示：按照概率学来说，4个字母在不出现重复字母的的排列组合总计4*3*2*1=24种。并利用char与int之间的关系，循环int值，转换为char输出
for (char i = 65; i <= 68; i++) {
for (char j = 65; j <= 68; j++) {
if (i == j) {
continue;
}
for (char k = 65; k <= 68; k++) {
if (k == i || k == j) {
continue;
}
for (char h = 65; h <= 68; h++) {
if (h == i || h == j || h == k) {
continue;
}
System.out.print(i);
System.out.print(j);
System.out.print(k);
System.out.print(h);
System.out.println();
}
}
}
}