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3月23日

zhyuzh3d 2022-03-24 阅读 67
java
package com.qiku.day18;

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

public class Zuo01 {
    public static void main(String[] args) {
        //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。
        int[] arr = new int[10];
        for (int i = 0; i < arr.length; i++) {
            arr[i] = (int) (Math.random()*99+1);
        }
        System.out.println(Arrays.toString(arr));

        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < arr.length; i++) {
            if (arr[i] >= 10){
                list.add(arr[i]);
            }
        }
        System.out.println(list);

    }
}

package com.qiku.day18;

import java.util.*;

public class Zuo02 {
    public static void main(String[] args) {
        //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。

        String[] strs ={"12345","67891","12347809933","98765432102","67891","12347809933"};
        Set<String> set = new HashSet<>();
        for (int i = 0; i < strs.length; i++) {
            set.add(strs[i]);
        }
        System.out.println(set);
        List<String> list = new LinkedList<>();
        Iterator<String> it = set.iterator();
        while (it.hasNext()){
            list.add(it.next());
        }
        System.out.println("迭代器:"+list);
        System.out.print("增强for循环:");
        for (String str: list){
            System.out.print(" "+str);

        }


    }
}

package com.qiku.day18;

public class Student implements Comparable<Student>{
    private String name;
    private int  age;
    private float score;
    public Student(String name, int age, float score) {
        this.name = name;
        this.age = age;
        this.score = score;
    }
    @Override
    public int compareTo(Student o) {
        if (this.score == o.score){
            return this.age - o.age;
        }
        return   o.score - this.score > 0 ? 1 : -1;
    }
    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", score=" + score +
                '}';
    }

    public String getName() {return name;}

    public void setName(String name) {this.name = name;}

    public int getAge() {return age;}

    public void setAge(int age) {this.age = age;}

    public float getScore() {return score;}

    public void setScore(float score) {this.score = score;}


}
package com.qiku.day18;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

public class Zuo03 {
    public static void main(String[] args) {
        //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。
        Student stu1 = new Student("liusan", 20, 90);
        Student stu2 = new Student("lisi",22,90);
        Student stu3 = new Student("wangwu",20,99);
        Student stu4 = new Student("sunliu",22,100);
        List<Student> list = new ArrayList<>();
        list.add(stu1);
        list.add(stu2);
        list.add(stu3);
        list.add(stu4);
        System.out.println(list);
        Collections.sort(list);
        System.out.println(list);



    }
}

package com.qiku.day18;

import java.util.*;

public class Zuo04 {
    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");
        map.remove(1);//根据key删除元素
        map.put(2,"周林");
        System.out.println(map);


        System.out.println("============");
        //1
        Set<Integer> keys = map.keySet();
        Iterator<Integer> itKey = keys.iterator();
        while (itKey.hasNext()){
            Integer key = itKey.next();
            String value = map.get(key);
            System.out.println(key+":"+value);
        }
//2
        Collection<String> values = map.values();
        Iterator<String> valueIt = values.iterator();
        while (valueIt.hasNext()){
            String value = valueIt.next();
            System.out.println(value);
        }

        //3 通过遍历所有的enter 遍历map
        //
        Set < Map.Entry < Integer,String > > entries = map.entrySet();
        Iterator<Map.Entry<Integer,String>>entryIt = entries.iterator();
        while (entryIt.hasNext()){
            Map.Entry<Integer,String> entry = entryIt.next();
            Integer key = entry.getKey();
            String value = entry.getValue();
            System.out.println(key+":"+value);
        }
    }
}

package com.qiku.day18;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

public class Zuo05 {
    public static void main(String[] args) {
        /**
         * 5、已知有十六支男子足球队参加2020 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
         *   2020 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
         */
        String[] strs = {" 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"};
        List<String> list1 = new ArrayList<>();
        List<String> list2 = new ArrayList<>();
        List<String> list3 = new ArrayList<>();
        List<String> list4 = new ArrayList<>();
        List<String> list = new ArrayList<>();
        for (int i = 0; i < strs.length; i++) {
            list.add(strs[i]);
        }
        System.out.println(list);
        for (int i = 0;i < strs.length;i++){
            int index = (int) (Math.random()*list.size());
            if(i<4){
                list1.add(list.get(index));
                list.remove(list.get(index));
            } if(i>=4 && i<8){
                list2.add(list.get(index));
                list.remove(list.get(index));
            } if(i>=8 && i<12){
                list3.add(list.get(index));
                list.remove(list.get(index));
            } if(i>=12 && i<16){
                list4.add(list.get(index));
                list.remove(list.get(index));
            }
        }
        System.out.println(list1);
        System.out.println(list2);
        System.out.println(list3);
        System.out.println(list4);
    }
}
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