快乐数问题

public static int func(int n){
        int sum = 0;
        while(n>0){
        int dig = n%10;
        sum+=dig*dig;
        n/=10;
        }
        return sum; 
    }
    public boolean isHappy(int n) {
        int slow = n;
        int fast = func(n);
        while(slow!=fast){
            slow = func(slow);
            fast = func(func(fast));
        }
        return slow ==1;