java 实现布隆数

package test;

import java.util.Arrays;
import java.util.BitSet;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * @author gjp
 * @className Filter class
 * @date 2021/12/31
 * @description: 布隆数
 */
public class Filter {
    //后面hash函数会用到，用来生成不同的hash值，可以随便给，但别给奇数
    private final int[] ints = {6, 8, 16, 38, 58, 68};
    private AtomicInteger currentBeanCount = new AtomicInteger(0);
    //布隆过滤器容量
    private int DEFAULT_SIZE = Integer.MAX_VALUE;
    //bit数组，用来存放结果
    private final BitSet bitSet = new BitSet(DEFAULT_SIZE);

    public BitSet getBitSet() {
        return bitSet;
    }

    public Filter() {
    }

    public Filter(int size) {
        if (size > Integer.MAX_VALUE) {
            throw new RuntimeException("size is too large");
        }
        if (size <= (2 << 8)) {
            throw new RuntimeException("size is too small");
        }
        DEFAULT_SIZE = size;
    }

    //获取当前过滤器的对象数量
    public Integer getCurrentBeanCount() {
        return currentBeanCount.get();
    }

    //计算出key的hash值，并将对应下标置为true
    public void push(Object key) {
        Arrays.stream(ints).forEach(i -> bitSet.set(hash(key, i)));
        currentBeanCount.getAndIncrement();
    }


    //计算出key的hash值，并将对应下标置为false
    public void del(Object key) {
        Arrays.stream(ints).forEach(i -> bitSet.clear(hash(key, i)));
        currentBeanCount.getAndDecrement();
    }

    //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 contain(Object key) {
        boolean result = true;
        for (int i : ints) {
            result = result && bitSet.get(hash(key, i));
        }
        return result;
    }

    //hash算法
    private int hash(Object key, int i) {
        int h;
        int index = key == null ? 0 : (DEFAULT_SIZE - 1 - i) & ((h = key.hashCode()) ^ (h >>> 16));
        return index > 0 ? index : -index;
    }


    public static void main(String[] args) {
        long start = System.currentTimeMillis();
        Filter myFilter = new Filter();
        myFilter.push("孙悟空");
        myFilter.push("孙悟空");
        myFilter.push("孙悟空");
        myFilter.push("二师兄");
        myFilter.push("沙师弟");
        myFilter.push(666);

        String pre = "唐僧1200";
        for (int i = 0; i <2 ; i++) {
            myFilter.push(pre+i);
        }
        System.out.println(";size="+myFilter.getCurrentBeanCount());
        System.out.println(myFilter.contain("孙悟空"));//true
        //删除
        myFilter.del("孙悟空");
        System.out.println("删除后：size="+myFilter.getCurrentBeanCount());

        System.out.println(myFilter.contain("孙悟空"));//false

        System.out.println(myFilter.contain("孙悟空"));//false

        System.out.println(myFilter.contain("二师兄"));//true
        System.out.println(myFilter.contain("二师兄1"));//false
        System.out.println(myFilter.contain(666));//true
        System.out.println(myFilter.contain("沙师弟"));//false

        System.out.println(myFilter.contain("唐僧200"));
        System.out.println(myFilter.contain("唐僧2000"));
        for (int i = 0; i <2 ; i++) {
            System.out.println(myFilter.contain(pre+i));
        }

        System.out.println((System.currentTimeMillis()-start) +"毫秒");



    }
}