java迭代法--素数，阶乘，最大公约数，最小公倍数

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package test;

public class PrimeTest {
    public static void main(String [] args) {
        //方法一
        System.out.println(primeBreak(84));
        //方法二
        System.out.println(f(84));
    }
    public static String primeBreak(int num) {
    //System.out.println(isPrime(num));
    //is prime
    if(isPrime(num)) {
       return num+"";
    }
    //is not prime
    else {
       for(int a = 2; a < num; a++) {
        for(int b = 2; b < num; b++) {
         while( a*b == num){
          return primeBreak(a) + "*" + primeBreak(b);
         }
        }
       }
    }
    return "ok";
    }
    public static boolean isPrime(int index) {

    boolean f = true;

    for(int j=2; j<index; j++) {
       if(index%j == 0) {
        f = false;
        break;
       }
    }
    if(!f) {
       return false;
    }
    else{
       return true;
    }
    }

    //Chengxusan(int n) {
        // String s="";
    //   int n=0;
        /* try{
          BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
                System.out.print("请输入一个数：");
                s = in.readLine();
                n =Integer.parseInt(s);
                System.out.println(""+f(n));
         }catch (IOException e){}
        }*/
         public   static String f(int n){
          for(int i=2;i<=n;i++){
          while(n!=i){

          if(n%i==0){
           return i+"*"+f(n/i);
           }
           else
            break;
          }
         }
          return ""+n;
        }
    }

public class Test {

    public static void main(String[] args) {
        System.out.println(gongyue(10, 12));
    }

   //迭代n的阶乘
    public static int method(int n) {
        if (n == 1) {
            return 1;
        } else {
            return n * method(n - 1);
        }
    }

    // 求m和n的最大公约数
    public static int gongyue(int m, int n) {
        while (m % n != 0) {
            int temp = m % n;
            m = n;
            n = temp;
        }
        return n;
    }

    // 求m和n的最小公倍数
    public static int gongbei(int m, int n) {
        return m * n / gongyue(m, n);
    }
}