java中list或数组中随机子集工具类

 

package com.example.demo.test;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Random;
import java.util.concurrent.ThreadLocalRandom;

/**
 * @author niunafei
 * @function
 * @email niunafei0315@163.com
 * @date 2018/12/23  下午1:17
 */
public class RandomUtils {

    /**
     * 从list 中获取制定个数的子串
     *
     * @param tl
     * @param n
     * @param <T>
     * @return
     */
    public static <T> List randomSub(List<T> tl, int n) {
        int count = tl.size()>n?n:tl.size();
        Random r = ThreadLocalRandom.current();
        //避免修改原列表
        List<T> temp = new ArrayList<>(tl);
        //记录返回列表
        List<T> list = new ArrayList<>(count);
        for (int i=0;i<count;i++) {
           int t=r.nextInt(temp.size());
            list.add(temp.get(t));
            temp.remove(t);
        }
        return list;
    }


    /**
     * 数组中获取指定个数的子串
     * @param t
     * @param n
     * @param <T>
     * @return
     */
    public static <T>T[] randomSub(T[] t,int n){
        List<T> list=randomSub(Arrays.asList(t),n);
        return list.toArray(Arrays.copyOf(t,list.size()));
    }




    public static void main(String[] args){
        List<Integer> list =new ArrayList<>(Arrays.asList(1,2,3,4,5,6,7,8,9,0,12,35,46,54,1,2,3,45,6,7,89,0));
        System.out.println("原始："+list);
        System.out.println("随机10"+randomSub(list,10));
        System.out.println("原始："+list);
        Integer[] array={1,2,3,4,5,6,7,8,9,0,12,35,46,54,1,2,3,45,6,7,89,0};
        //使用Arrays.asList();将数组转为list
        System.out.println("原始数组"+Arrays.asList(array));
        System.out.println("数组随机10"+Arrays.asList(randomSub(array,10)));
        System.out.println("原始数组"+Arrays.asList(array));
    }
}


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