本文主要是介绍java权重随机算法，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
Pair:
package com.ruoyi.receipt.domain;/*** 表示选项和权重的类Pair*/
public class Pair {Object item;double weight;public Pair(Object item, double weight) {this.item = item;this.weight = weight;}public Object getItem() {return item;}public double getWeight() {return weight;}
}
WeightRandom:
package com.ruoyi.receipt.domain;import java.util.Arrays;
import java.util.Random;/*** 带权重的选择WeightRandom*/
public class WeightRandom {private Pair[] options;private double[] cumulativeProbabilities;private Random rnd;public WeightRandom(Pair[] options) {this.options = options;this.rnd = new Random();prepare();}/*** prepare()方法计算每个选项的累计概率，保存在数组cumulativeProbabilities中*/private void prepare() {int weights = 0;for (Pair pair : options) {weights += pair.getWeight();}cumulativeProbabilities = new double[options.length];int sum = 0;for (int i = 0; i < options.length; i++) {sum += options[i].getWeight();cumulativeProbabilities[i] = sum / (double) weights;}}/*** nextItem()方法根据权重随机选择一个，具体就是，首先生成一个0～1的数，* 然后使用二分查找，如果没找到，返回结果是-（插入点）-1，所以-index-1就是插入点，插入点的位置就对应选项的索引。* @return*/public Object nextItem() {double randomValue = rnd.nextDouble();int index = Arrays.binarySearch(cumulativeProbabilities, randomValue);if (index < 0) {index = -index - 1;}return options[index].getItem();}public static void main(String[] args) {Pair[] options = new Pair[]{new Pair(123L, 1), new Pair(456L, 2), new Pair(789L, 3)};WeightRandom rnd = new WeightRandom(options);for (int i = 0; i < 10; i++) {System.out.print(rnd.nextItem() + " ");}}}
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