根据概率抽奖（无奖品数量） -- Java实现

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import java.math.BigDecimal;import java.util.ArrayList;import java.util.Arrays;import java.util.List;/** * @PACKAGE_NAME.Test  * 日期： 2017/5/3 * 描述： */public class Test {    /**     * 所有所有奖品     */    public enum Trophy {        A("奖品-A", new BigDecimal(0.889)),        B("奖品-B", new BigDecimal(0.1)),        C("奖品-C", new BigDecimal(0.01)),        D("奖品-D", new BigDecimal(0.001)),;        public String name;        public BigDecimal probably;        Trophy(String name, BigDecimal probably) {            this.name = name;            this.probably = probably;        }    }    /**     * 获取一个随机数     *     * @param min 最大值     * @param max 最小值     * @return     */    public int getRandomInt(int min, int max) {        return (int) Math.round(Math.random() * (max - min) + min);    }    /**     * 获取随机数的最大值     *     * @param trophies 所有奖品     * @return     */    public int getMaxRandomInt(List<Trophy> trophies) {        BigDecimal minProbably = trophies.stream().min((x, y) -> x.probably.compareTo(y.probably)).get().probably;        String[] split = (minProbably.doubleValue() + "").trim().split("\\.");        return (int) Math.pow(10, split[split.length - 1].length());    }    /**     * 抽奖     *     * 随机一个数，判断在哪个奖品的区间内     *     * @return     */    public Trophy draw() {        Trophy trophy = null;        int maxInt = getMaxRandomInt(Arrays.asList(Trophy.values()));        int random = getRandomInt(1, maxInt), start = 0;        for (Trophy trophy1 : Trophy.values()) {            int end = start + (int) (trophy1.probably.doubleValue() * maxInt);            if (random > start && random <= end) {                trophy = trophy1;                break;            } else {                start = end;            }        }        return trophy;    }    @org.junit.Test    public void test() {        List<Trophy> trophyList = new ArrayList<>();        for (int i = 0; i < 10000; i++) {            Trophy trophy = draw();            if (trophy != null) {                trophyList.add(trophy);            }        }        //计算各个抽中次数        for (Trophy trophy : Trophy.values()) {            System.out.println("抽中 " + trophy.name + " 数量："                    + trophyList.stream().filter(trophy1 -> trophy1.equals(trophy)).count());        }    }}
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