按一定几率产生天气状况

public class WeatherUtil {
/**
* 2种天气情况.
*/
private String[] weathers = { "sunny", "rain" };

/**
* 每种天气情况对应的几率
*/
private int[] rates;

/**
* 数轴
*/
private List<Integer> list = new ArrayList<Integer>();

/**
* 计算数轴上的点
*
* @param j
* @return
*/
private int getRandomRate(int j) {
int rate = 0;
for (int i = 0; i < j; i++) {
rate = rate + rates[i];
}
return rate;
}

/**
* 构造一个数轴，每个选项对应一个区间
*/
private void init(int[] sysWeathersPercent) {
this.rates = sysWeathersPercent;
list.add(0);
for (int i = 0; i < weathers.length; i++) {
list.add(getRandomRate(i + 1));
}
}

/**
* 使用Math 的random 方法产生一个0--100 的随机数种子，判断其落在那个区间上.返回该区间对应的天气.
*
* @return
*/
public String getChoice(int[] sysWeathersPercent) {
init(sysWeathersPercent);
String weather = "";
int random = (int) (100 * Math.random());
for (int i = 0; i < weathers.length; i++) {
if (list.get(i) <= random && random < list.get(i + 1)) {
weather = weathers[i];
break;
}
}
return weather;
}
}