思想

统计

统计思想:利用map集合进行统计

遍历

遍历集合，按照指定的集合进行拼接的两种方式：
- StringBuilder
- StringJoiner

概率问题

如30%的甲，70%的乙：
1. 创建一个新的集合：赋30%的”1”，赋70%的”2”
2. 对所创建的集合元素进行随机取值：Random r = new Random();
3. 对随机取得的值进行条件判断，取到的值就有概率

package CS408.CollectionText;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Random;

public class Text2 {
    //班级里有N个学生要求:70%的概率随机到男生,30%的概率随机到女生
    public static void main(String[] args) {
        //创建集合
        ArrayList<Integer> list = new ArrayList<>();
        //添加元素
        Collections.addAll(list,1,1,1,1,1,1,1);
        Collections.addAll(list,0,0,0);
        //从list中抽取1,0
        Random r = new Random();
        int index = r.nextInt(list.size());
        int number = list.get(index);

        //创建两个集合分别存储男生与女生
        ArrayList<String> boyList = new ArrayList<>();
        ArrayList<String> girlList = new ArrayList<>();

        Collections.addAll(boyList,"男1","男2","男3","男4","男5","男6","男7","男8","男9");
        Collections.addAll(girlList,"女1","女2","女3","女4","女5","女6","女7","女8");

        //判断此时是从boyList里抽取，还是从girlList中抽取
        if (number == 1){
            int boyIndex = r.nextInt(boyList.size());
            String name = boyList.get(boyIndex);
            System.out.println(name);
        }else {
            int girlIndex = r.nextInt(girlList.size());
            String name = girlList.get(girlIndex);
            System.out.println(name);
        }
    }
}