java 权重随机算法实现

import java.util.*;

/**

 * 权重随机算法实现

 * a b c d 对应权重范围 --- [0,1)、[1,3)、[3,6)、[6,10)

 */

public class RandomSF {

    private static TreeMap<String, Integer> hm = new TreeMap<>();

    public static void main(String[] args) throws Exception {

        TreeMap<String, Integer> randomMap = new TreeMap<String, Integer>();

        randomMap.put("a", 1);

        randomMap.put("b", 2);

        randomMap.put("c", 3);

        randomMap.put("d", 4);

        Integer tmp = 0;

        ArrayList<ElementWeight> arr = new ArrayList<ElementWeight>();

        for (Map.Entry<String, Integer> entry : randomMap.entrySet()) {

            String key = entry.getKey();

            Integer value = entry.getValue();

            ElementWeight ew = new ElementWeight(key, tmp, tmp + value);

            tmp += value;

            arr.add(ew);

        }

        Random random = new Random();

        for (int j = 0; j < 100000000; j++) {

            int i = random.nextInt(tmp);

            String randomStr = binarySearch(arr, i);

            countRandomStr(randomStr);

        }

        for (ElementWeight ew:arr) {

            System.out.println(ew.getElement()+"的权重范围:"+"["+ew.getLow()+","+ew.getHigt()+")");

        }

        System.out.println(hm);

    }

//    二分查找实现

    public static String binarySearch(ArrayList<ElementWeight> arr, int num) {

        int high = arr.size();

        int low = 0;

        while (high >= low) {

            int middle = (high + low) / 2;

            ElementWeight ew = arr.get(middle);

            if (num >= ew.getLow() && num < ew.getHigt()) {

                return ew.getElement();

            } else if (num >= ew.getHigt()) {

                low = middle + 1;

            } else if (num < ew.getLow()) {

                high = middle - 1;

            }

        }

        return null;

    }

//  权重元素实体类

    static class ElementWeight {

        private String element;

        private Integer low;

        private Integer higt;

        public ElementWeight(String element, Integer low, Integer higt) {

            this.element = element;

            this.low = low;

            this.higt = higt;

        }

        public String getElement() {

            return element;

        }

        public Integer getLow() {

            return low;

        }

        public Integer getHigt() {

            return higt;

        }

    }

//  统计随机string的个数

    public static void countRandomStr(String str) {

        Integer value = hm.get(str);

        if (value == null) {

            hm.put(str, 1);

        } else {

            hm.put(str, ++value);

        }

    }

}