3.23works

package com.qiku.yrc.work;

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

public class W1 {
   // 1、产生10个1-100的随机数，并放到一个数组中，
    public static void main(String[] args) {
        List list=new ArrayList();
         int[] arr=new int[10];
        for (int i = 0; i < arr.length; i++) {
            int x =(int)(Math.random()*99+1);
            if (x>10){
          list.add(x);
            }
            arr[i]=x;
        }
        for (int i = 0; i < list.size(); i++) {
            System.out.println(list.get(i));
        }
    }
}

package com.qiku.yrc.work;
//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。


import java.util.*;

public class W2 {
    public static void main(String[] args) {
        Collection c1=  new ArrayList();
        String[] strs ={"12345","67891","12347809933","98765432102",
                "67891","12347809933"};
        LinkedList<String> linkedList = new LinkedList<String>();
        for (int i = 0; i < strs.length; i++) {
            linkedList.add(strs[i]);
        }
        Set set = new HashSet(linkedList);
        linkedList.clear();
        linkedList.addAll(set);
        System.out.println(linkedList);
        System.out.println("迭代器：");
        Iterator it = linkedList.iterator();
        while (it.hasNext()){
            //it.hasNext()
            Object num = it.next();     //可用obj接收

                System.out.print(" "+num);
            }
        //增强for循环
        System.out.println();
        System.out.println("增强for循环：");
        for (Object obj :linkedList){
            System.out.print(obj+" ");
        }
        }

    }

package com.qiku.yrc.work;

import java.util.*;

public class W3 {
    //3、用Comparable接口对下列四位同学的成绩做降序排序，
    // 如果成绩一样，那在成绩排序的基础上按照年龄由小到大排序。
    //提示：
    //编写一个Student类用来实现Comparable<Student>接口,并
    // 在其中重写CompareTo(Student o)方法　
    public static void main(String[] args) {
        List<Student> list  =new ArrayList<>();
        Collection c1 = new ArrayList();
        Student  s1= new Student("liusan",20,90.0f);
        Student  s2= new Student("liusan",22,90.0f);
        Student  s3= new Student("liusan",20,99.0f);
        Student  s4= new Student("liusan",22,100.0f);
        list.add(s1);
        list.add(s2);
        list.add(s3);
        list.add(s4);
        Collections.sort(list, new Comparator<Student>() {
            @Override
            public int compare(Student o1, Student o2) {
                if (o1.score == o2.score){
                    return o1.age - o2.age;
                }

                return (int) (o2.score - o1.score);
            }
        });
        for (Student s : list){
            System.out.println(s);
        }
    }
}



class Student implements Comparable<Student>{
    String name;
    int age;
    float score;

    public Student(String name, int age, float score) {
        this.name = name;
        this.age = age;
        this.score = score;
    }



    public Student() {
    }

    @Override
    public int compareTo(Student o) {
        if (this.score == o.score){
            return this.age - o.age;
        }

        return (int) (o.score - this.score);
    }

    @Override
    public String toString() {
        return this.name + "["+ this.age +"]:" + this.score;
    }
}

package com.qiku.yrc.work;

import java.util.HashMap;
import java.util.Map;

public class W4 {
    /**
     * 4、现在有一个map集合如下：
     * Map<Integer,String> map = new HashMap<Integer, String>();
     *         map.put(1, "张三丰");
     *         map.put(2, "周芷若");
     *         map.put(3, "汪峰");
     *         map.put(4, "灭绝师太");
     * 要求：
     * 1.遍历集合，并将序号与对应人名打印。
     * 2.向该map集合中插入一个编码为5姓名为李晓红的信息
     * 3.移除该map中的编号为1的信息
     * 4.将map集合中编号为2的姓名信息修改为"周林"
     * ————————————————
     *
     *
     */
    public static void main(String[] args) {
        Map<Integer,String> map = new HashMap<Integer, String>();
             map.put(1, "张三丰");
             map.put(2, "周芷若");
             map.put(3, "汪峰");
             map.put(4, "灭绝师太");
        System.out.println(map);
        map.put(5,"李晓红");
        System.out.println(map);
        map.remove(1);
        System.out.println(map);
        map.replace(2,"周林");
        System.out.println(map);

    }
}

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

public class W5 {
    public static void main(String[] args) {
        List<String> list1 = new ArrayList<>();
        List<String> list2 = new ArrayList<>();

        String [] str = {"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<str.length;i++) {
            list1.add(str[i]);
        }
        while(true) {
            //将l2清零
            list2.clear();
            while(true) {
                //产生0-最大下标的随机数
                int a = (int)(Math.random()*list1.size());
                //拿l中出来一个字符串
                String s =list1.get(a);
                //把这个字符串放进l2中
                list2.add(s);
                //把这个字符串从l移除
                list1.remove(a);
                //当l2等于4的时候打印这4个字符串，跳出循环
                if(list2.size()==4) {
                    for(String s2:list2) {
                        System.out.print(s2+"  ");
                    }
                    break;
                }
            }
            System.out.println();
            //当l中元素拿完的时候跳出循环
            if(list1.size()==0) {
                break;
            }
        }
    }
}