[102.2 MID] 2. 亂數產生器

2.(100%)亂數產生器
    請實作如下兩亂數產生方法
	public static int randomIntegerFromInterval(int lower, int upper)
	回傳範圍介於[lower,upper]區間內的一個均勻隨機整數.
	提示: 利用Math.random()產生一個介於[0,1)區間之隨機實數x,
	      再用如下公式,將rand範圍放大調整到[a,b]區間,
	      	    int rand = a + (int) (x * (b-a+1));

	public static char randomGender(int menWeight, int womenWeight)
	回傳一個隨機男(M)或女(F)性別表示字元,其男女人數權重比為menWeight : womenWeight
	提示: 利用randomIntegerFromInterval(1, menWeight+womenWeight)
	      產生一個[1,menWeight+womenWeight]隨機整數y,
	      若y位於[1,menWeight]區間,回傳男(M)字元;
	      若y位於[menWeight+1,menWeight+womenWeight]區間,回傳女(F)字元;

(Sample Output)
600 numbers from interval [-3,2] are -2, 0, -1, 2, -3, 1, ...
    frequency of -3 is ?
    frequency of -2 is ?
    ...

500 genders with weight (men,women)=(4,1) are M, M, F, M, ...
    frequency of M is ?
    frequency of W is ?