java实现list均匀采样算法

功能说明：从一个List对象中均匀抽选出固定数量的样本。

import lombok.Getter;

import java.util.LinkedList;
import java.util.List;

public abstract class Sample {

    //样本数据
    protected List sampleData;
    //抽取的样本数
    protected int sampleTotal;
    @Getter
    //采样的元素索引
    protected List sampleIndex;
    public abstract void execute();
    public void sample(){
        if(sampleTotal <= 0){
            throw new IllegalArgumentException("采样参数不正确");
        }
        if(sampleData.size() <= sampleTotal){
            for (int i = 0; i < sampleData.size(); i++) {
                sampleIndex.add(i);
            }
        }else{
            this.execute();
        }
    }

    public List getResult() {
        List result = new LinkedList<>();
        for (Integer i : sampleIndex) {
            result.add(sampleData.get(i));
        }
        return result;
    }

}

package com.zhou.chart.util;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * 实现均匀采样(保留首尾)
 * @author lang.zhou
 * @date 2022/6/23 14:34
 */
public class HeadTailSample extends Sample{


    public HeadTailSample(List sampleData, int sampleTotal) {
        this.sampleData = sampleData;
        this.sampleTotal = sampleTotal;
        this.sampleIndex = new ArrayList<>(sampleTotal);
    }

    public void execute(){
        int size = sampleData.size();
        float sec = (size+0.0f)/(sampleTotal - 1);
        if(size <= sampleTotal){

            return;
        }
        sampleIndex.add(0);
        float mark = sec;
        for (int i = 1; i < size; i++) {
            float cu = i + 0.0f;
            float rate = Math.abs(mark - cu);
            //补偿因子
            if(rate < 1){
                sampleIndex.add(i);
                //保证采样数量不多于sampleTotal
                if(sampleIndex.size()>= sampleTotal){
                    break;
                }
                mark+= sec;
            }
        }
        if(!sampleIndex.contains(size - 1)){
            if(sampleIndex.size()>= sampleTotal){
                sampleIndex.remove(sampleIndex.size() - 1);
            }
            sampleIndex.add(size - 1);
        }
    }

    public static void main(String[] args) {
        //5
        test(3,1,2,3,4,5,6,7,8);
        test(5,1,2,3,4,5);
        test(5,1,2,3,4,5,6);
        test(5,1,2,3,4,5,6,7);
        test(5,1,2,3,4,5,6,7,8);
        test(5,1,2,3,4,5,6,7,8,9);
        test(5,1,2,3,4,5,6,7,8,9,10);
        test(5,1,2,3,4,5,6,7,8,9,10,11);
        test(5,1,2,3,4,5,6,7,8,9,10,11,12);
        test(5,1,2,3,4,5,6,7,8,9,10,11,12,13);
        test(5,1,2,3,4,5,6,7,8,9,10,11,12,13,14);
        test(5,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15);
    }
    private static void test(int cnt,Integer ... a){
        List l = Arrays.asList(a);
        Sample sample = new HeadTailSample<>(l, cnt);
        sample.sample();
        List list = sample.getResult();
        System.out.println(Arrays.toString(list.toArray()));
    }
}

public abstract class Sample {

    //样本数据
    protected List sampleData;
    //抽取的样本数
    protected int sampleTotal;
    @Getter
    //采样的元素索引
    protected List sampleIndex;
    public abstract void execute();
    public void sample(){
        if(sampleTotal <= 0){
            throw new IllegalArgumentException("采样参数不正确");
        }
        if(sampleData.size() <= sampleTotal){
            for (int i = 0; i < sampleData.size(); i++) {
                sampleIndex.add(i);
            }
        }else{
            this.execute();
        }
    }

    public List getResult() {
        List result = new LinkedList<>();
        for (Integer i : sampleIndex) {
            result.add(sampleData.get(i));
        }
        return result;
    }

}

运行结果：