java集合练习题

1.产生10个1-100的随机数，并放到一个数组中，把数组中大于等于10的数字放到一个list集合中，并打印到控制台。

public class Test01 {
    public static void main(String[] args) {
        Random random=new Random();
        List list=new ArrayList();
        int[] ints=new int[10];
        for (int i = 0; i <ints.length ; i++) {
            ints[i]=random.nextInt(100)+1;
            if (ints[i]>=10){
                list.add(ints[i]);
            }
        }
        System.out.println(Arrays.toString(ints));
        System.out.println(list);

    }
}

2.已知数组存放一批QQ号码，QQ号码最长为11位，最短为5位String[] strs = {"12345","67891","12347809933","98765432102","67891","12347809933"}。将该数组里面的所有qq号都存放在LinkedList中，将list中重复元素删除，将list中所有元素分别用迭代器和增强for循环打印出来。

 

public class Test02 {
    public static void main(String[] args) {
        String[] strs = {"12345","67891","12347809933","98765432102","67891","12347809933"};
        LinkedList list=new LinkedList();
        for (int i = 0; i <strs.length ; i++) {
            list.add(i,strs[i]);
        }
        System.out.println(list);
        for (int i = 0; i <list.size() ; i++) {
            String str= (String) list.get(i);
            for (int j=i+1;j<list.size();j++){
                if (str.equals(list.get(j))){
                    list.remove(j);
                }
            }
        }
        System.out.println(list);
    }
}

 

 

3.定义一个泛型为String类型的List集合，统计该集合中每个字符 （注意，不是字符串）出现的次数。例如：集合中有”abc”、”bcd”两个元素， 程序最终输出结果为：“a = 1,b = 2,c = 2,d = 1”。

public class Test03 {
    public static void main(String[] args) {
        List<String> list=new ArrayList<>();
        String[] strings={"asd","qwe","aaa","sdz"};
        for (int i = 0; i <strings.length ; i++) {
            list.add(i,strings[i]);
        }
        System.out.println(list);
        List<Character> list1=new ArrayList<Character>();
        for (String s:strings){
            for (int i = 0; i <s.length() ; i++) {
                list1.add(s.charAt(i));
            }
        }
        System.out.println(list1);
        for (int i = 0; i <list1.size() ; i++) {
            int num=1;
            for (int j=i+1;j<list1.size();j++){
                if (list1.get(i).equals(list1.get(j))){
                    list1.remove(j);
                    num++;
                }
            }
            System.out.println(list1.get(i)+"\t"+num);
        }

    }
}

4.已知有十六支男子足球队参加2008 北京奥运会。写一个程序，把这16 支球队随机分为4 个组。采用List集合和随机数  2008 北京奥运会男足参赛国家： 科特迪瓦，阿根廷，澳大利亚，塞尔维亚，荷兰，尼日利亚、日本，美国，中国，新西 兰，巴西，比利时，韩国，喀麦隆，洪都拉斯，意大利

public class Grouping {
    public static void main(String[] args) {
        List list=new ArrayList();
        Random random=new Random();
        String[] strings={ "科特迪瓦","阿根廷","澳大利亚","塞尔维亚","荷兰",
        "尼日利亚","日本","美国","中国","新西兰","巴西","比利时","韩国","喀麦隆","洪都拉斯","意大利"};
        for (int i = 0; i < strings.length; i++) {
            list.add(i,strings[i]);
        }
        System.out.println(list);
        for (int i = 0; i < 4; i++)
        {
            System.out.println("第" + (i + 1) + "组是：");
            for (int j = 0; j < 4; j++)
            {
                String sg;
                sg = (String) list.get(random.nextInt(list.size()));
                System.out.print(sg + " ");
                list.remove(sg);
            }
            System.out.println("\n");

        }
    }
}

5.传入当前时间，返回该时间是周几，中文显示（星期一）

public class GetWeekOfDate {
    public static void main(String[] args) {
        Calendar calendar=Calendar.getInstance();
        int day=calendar.get(Calendar.DAY_OF_WEEK);
        ArrayList week=new ArrayList();
        week.add(0,"星期日");
        week.add(1,"星期一");
        week.add(2,"星期二");
        week.add(3,"星期三");
        week.add(4,"星期四");
        week.add(5,"星期五");
        week.add(6,"星期六");
        System.out.println(week.get(day-1));

    }
}