随机点名器_带概率,不重复

public class test1 {
    public static void main(String[] args) {
        //随机点名器
        ArrayList<String> list=new ArrayList<>();
        Collections.addAll(list,"xiangxiang","baby","haha","xixi","nono","yesyes");
        Random r=new Random();
        int index=r.nextInt(list.size());
        String name=list.get(index);
        System.out.println(name);
        //或者是
        Collections.shuffle(list);
        System.out.println(list.get(0));
    }
}
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public class test2 {
    public static void main(String[] args) {
        //带概率的随机点名器
        ArrayList<Integer> list1=new ArrayList<>();
        Collections.addAll(list1,1,1,1,1,1,1,1,0,0,0);
        //打乱集合
        Collections.shuffle(list1);
        int index=list1.get(0);
        //创建两个集合分别存储女生和男生的名字
        ArrayList<String> list2=new ArrayList<>();
        Collections.addAll(list2,"xiangxiang","nono","yesyes","qq","ww","ee","rr");
        ArrayList<String> list3=new ArrayList<>();
        Collections.addAll(list3,"haha","baby","xixi");
        Random r=new Random();
        if(index==1){
            int i = r.nextInt(list2.size());
            System.out.println(list2.get(i));
        }else{
            int i = r.nextInt(list3.size());
            System.out.println(list3.get(i));
        }
    }
}
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public class test3 {
    public static void main(String[] args) {
        //自动点名器
        //被点到的不会再点,直到所有学生都点到
        //再重新开启第二轮

        //创建集合存储全部学生姓名
        ArrayList<String> list = new ArrayList<>();
        Collections.addAll(list, "张三", "李四", "王五", "赵六", "田七", "宋八", "周九", "吴十");
        Random r = new Random();
        Scanner sc = new Scanner(System.in);
        while (true) {
            while(list.size()>0){
                System.out.println("请按回车开始点名");
                sc.nextLine();
                //随机索引
                int index = r.nextInt(list.size());
                //获取被点到的学生姓名
                String name = list.remove(index);
                System.out.println("被点到的学生是:"+name);
            }
            Collections.addAll(list,"张三", "李四", "王五", "赵六", "田七", "宋八", "周九", "吴十");
        }
    }
}

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集合嵌套
public class test4 {
    public static void main(String[] args) {
        Map<String,String> map=new HashMap<>();
        map.put("江苏省","南京市,扬州市,苏州市,无锡市,常州市");
        map.put("湖北省","武汉市,孝感市,十堰市,宜昌市,鄂州市");
        map.put("广东省","广州市,深圳市,珠海市,汕头市,佛山市");
        for (String s : map.keySet()) {
            System.out.println(s+"="+map.get(s));
        }
        System.out.println("-------------------");
        //第二种方式
        Map<String, ArrayList<String>> map1=new HashMap<>();
        ArrayList<String> city1=new ArrayList<>();
        Collections.addAll(city1,"南京市","扬州市","苏州市","无锡市","常州市");
        ArrayList<String> city2=new ArrayList<>();
        Collections.addAll(city2,"武汉市","孝感市","十堰市","宜昌市","鄂州市");
        ArrayList<String> city3=new ArrayList<>();
        Collections.addAll(city3,"广州市","深圳市","珠海市","汕头市","佛山市");
        map1.put("江苏省",city1);
        map1.put("湖北省",city2);
        map1.put("广东省",city3);
        for (String s : map1.keySet()) {
            //用的stringjoiner来去掉[]
            StringJoiner sj=new StringJoiner(",","","");
            for (String s1 : map1.get(s)) {
                sj.add(s1);
            }
            System.out.println(s+"="+sj);
        }
    }
}