布隆过滤器原理（小白都能看懂的demo）

先贴demo后BB

package com.jd.demo.test; import java.util.Arrays; import java.util.BitSet; import java.util.concurrent.atomic.AtomicBoolean; public class MyBloomFilter { //你的布隆过滤器容量 private static final int DEFAULT_SIZE = 2 << 28; //bit数组，用来存放结果 private static BitSet bitSet = new BitSet(DEFAULT_SIZE); //后面hash函数会用到，用来生成不同的hash值，可随意设置，别问我为什么这么多8，图个吉利 private static final int[] hashInts = {1, 6, 16, 38, 58, 68}; //add方法，计算出key的hash值，并将对应下标置为true public void add(Object key) { Arrays.stream(hashInts ).forEach(i -> bitSet.set(hash(key, i))); } //判断key是否存在，true不一定说明key存在，但是false一定说明不存在 public boolean isContain(Object key) { boolean result = true; for (int i : hashInts) { //短路与，只要有一个bit位为false，则返回false result = result && bitSet.get(hash(key, i)); } return result; } //hash函数，借鉴了hashmap的扰动算法，强烈建议大家把这个hash算法看懂，这个设计真的牛皮加闪电 private int hash(Object key, int i) { int h; return key == null ? 0 : (i * (DEFAULT_SIZE - 1) & ((h = key.hashCode()) ^ (h >>> 16))); } }

测试

public static void main(String[] args) { MyNewBloomFilter myNewBloomFilter = new MyNewBloomFilter(); myNewBloomFilter.add("张学友"); myNewBloomFilter.add("郭德纲"); myNewBloomFilter.add("蔡徐鸡"); myNewBloomFilter.add(666); System.out.println(myNewBloomFilter.isContain("张学友"));//true System.out.println(myNewBloomFilter.isContain("张学友 "));//false System.out.println(myNewBloomFilter.isContain("张学友1"));//false System.out.println(myNewBloomFilter.isContain("郭德纲"));//true System.out.println(myNewBloomFilter.isContain("蔡徐老母鸡"));//false System.out.println(myNewBloomFilter.isContain(666));//true System.out.println(myNewBloomFilter.isContain(888));//false }

概述 算球咯，没啥好说的，代码复制即可用，看十遍不如自己跑一遍，注释很详细了；

如果对上面的hash算法有疑惑，请移步帮你真正理解hashCode和hash算法

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ok我话讲完

嘤嘤嘤~