public?class?Test?{
????public?static?void?main(String[]?args)?{
????????getA(90);
????}
???
public?static?void?getA(int?number){
	???????String?str?=?"";
	???????int?i=2;
	???????for?(i=2;?i<number;?i++)?{
	???????????if(number?%?i?==?0?){
	???????????????str?+=?i?+?"*";
	??????????????number?=?number?/?i;
	??????????????i--;
	???????????}
	???????}
	???????str?+=?i;
	???????System.out.println(number?+?"質因數分解："?+str);
	???}

}

//用循環，因數范圍在2-num

?? for(i=2;?i<=num;?i++){

//整除是因子

?????? while(num%i==0)
???????? {
??????????? num=num/i;
? ????????? System.out.print(i+"*");
???????? }

}

詳細點