随机取得用户定义的整数实现

2012-07-19

随机获得用户定义的整数实现辅助类提供了3个方法：(1)addWeightNumber(int weight,int num):为某个num赋予w

随机获得用户定义的整数实现

辅助类提供了3个方法：

(1)addWeightNumber(int weight,int num):为某个num赋予weight权重，此权重代表此数字在随机获取时的获得概率；权重大，则获得的概率就大，权重小，则获得的概率就小。

(2)addWeightNumRange(int weight,int numfrom,int numto,int ... numExcludes);同时为连续多个数字赋予权重，最后这个参数可以排除例外数字，比如addWeightNumRange(5,1,10,5); 表示为1~10（除去5）的数字赋予权重5；

(3)getNextInt();在你赋予权重之后，此方法会随即在你赋予权重的这些数字之中取出一个；

优点：此方法和new Random().nextInt()的优势在于，可以为每个数字赋予权重，并且可以随机取出用户指定的数字集合；

package org.xiazdong.util;import java.util.ArrayList;import java.util.List;import java.util.Random;public class IntegerWeightRandom {private List<Integer> weights = new ArrayList<Integer>();private List<List<Integer>> numbers = new ArrayList<List<Integer>>();private Integer totalWeight;private Random random = new Random();public IntegerWeightRandom() {}private Integer getTotalWeight(){if(totalWeight == null){totalWeight = 0;for(Integer weight:weights){totalWeight += weight;}}return totalWeight;}/* * 为某个number赋予一个weight，可能一个weight对应多个numbers，因此List<Integer>weight中一个元素对应List<List<Integer>>numbers中的一个List<Integer> * *///此函数表示一个weight对应一个numberpublic void addWeightNumber(int weight,int num){weights.add(weight);List<Integer> list = new ArrayList<Integer>();list.add(num);numbers.add(list);}//此函数表示一个weight对应多个numberpublic void addWeightNumRange(int weight,int numFrom,int numTo,int...numExcludes){weights.add(weight);List<Integer> list = new ArrayList<Integer>();for(int i = numFrom;i <= numTo;i++){boolean exclude = false;for(int numExclude:numExcludes){if(i == numExclude){exclude = true;}}if(!exclude){list.add(i);}}numbers.add(list);}/* * 举例： * 如果数字8的weight为1，数字9的weight为2，则totalWeight=3，8的范围为(0,1],9的范围为[2,3]如果随机数为2，则在9的范围内 * *///此函数为随机取一个整数（按照权重概率取）public Integer getNextInt(){int weightRandom = random.nextInt(getTotalWeight());int weightCount = 0;for(int i = 0;i < weights.size();i++){int weight = weights.get(i);if(weightRandom >= weightCount && weightRandom < weightCount + weight){List<Integer> numList = numbers.get(i);if(numList.size() == 1){return numList.get(0);}int numRandom = random.nextInt(numList.size());return numList.get(numRandom);}weightCount += weight;}return null;}}

测试类：

package test.org.xiazdong.util;import org.junit.Test;import org.xiazdong.util.IntegerWeightRandom;public class IntegerWeightRandomTest {@Testpublic void testGetNextInt(){IntegerWeightRandom random = new IntegerWeightRandom();random.addWeightNumber(1, 0);random.addWeightNumber(5, 1);random.addWeightNumber(9, 2);random.addWeightNumber(15, 3);random.addWeightNumber(20, 4);random.addWeightNumber(30, 5);random.addWeightNumber(40, 7);random.addWeightNumber(50, 6);random.addWeightNumber(60, 8);random.addWeightNumber(70, 9);for(int i=0;i<10;i++){System.out.println(random.getNextInt());}}}

热点排行

编程

随机取得用户定义的整数实现