Java ArrayList集合案例（上课笔记）

package cn.hei.array;

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


public class Work01ArrayListRandom {
    public static void main(String[] args) {
        Random r = new Random();
        ArrayList list = new ArrayList<>();

        for (int i = 0; i < 6; i++) {
            int num = r.nextInt(33)+1;
            list.add(num);
        }

        for (int j = 0; j < list.size(); j++) {
            System.out.println(list.get(j));
        }
    }
}

package cn.hei.array;

public class Student {
    private String name;
    private int age;

    public Student() {
    }

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

    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;
    }
}

package cn.hei.array;

import java.util.ArrayList;


public class Work02ArrayListStudent {

    public static void main(String[] args) {
        ArrayList list = new ArrayList<>();

        Student one = new Student("张",12);
        Student two = new Student("王",22);
        Student three = new Student("李",14);
        Student four = new Student("士大夫",16);

        list.add(one);
        list.add(two);
        list.add(three);
        list.add(four);

        //遍历集合
        for (int i = 0; i < list.size(); i++) {
            Student stu = list.get(i);
            System.out.println("姓名："+stu.getName()+"年龄："+stu.getAge());
        }
    }
}

package cn.hei.array;

import java.lang.reflect.Array;
import java.util.ArrayList;


public class Work03ArrayListPrint {

    public static void main(String[] args) {
        ArrayList list = new ArrayList<>();
        list.add("张克斯");
        list.add("王扩大");
        list.add("李空间");
        list.add("方东方");
        System.out.println(list);//[张克斯, 王扩大, 李空间, 方东方]

       printArrayList(list);//{张克斯@王扩大@李空间@方东方}
    }
    
    public static void printArrayList(ArrayList list){
        //{1@3@4}
        System.out.print("{");
        for (int i = 0; i < list.size(); i++) {
            String name = list.get(i);
            if (i == list.size() - 1){
                System.out.println(name + "}");
            }else {
                System.out.print(name + "@");
            }

        }
    }
}

package cn.hei.array;

import jdk.nashorn.internal.runtime.arrays.ArrayLikeIterator;

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


public class Work04ArrayListReturn {

    public static void main(String[] args) {
        ArrayList bigList = new ArrayList<>();
        Random r = new Random();
        for (int i = 0; i < 20; i++) {
            int num = r.nextInt(100)+1;//1~100
            bigList.add(num);
        }
        ArrayList smallList = getSamllList(bigList);
        System.out.println("偶数总共有："+smallList.size());
        for (int i = 0; i < smallList.size(); i++) {
            System.out.println(smallList.get(i));
        }
    }
    //这个方法，接收大集合参数，返回小集合结果
    public static ArrayList getSamllList(ArrayList bigList){

        //创建一个小集合，用来装偶数结果
        ArrayList smallList = new ArrayList<>();
        for (int i = 0; i < bigList.size(); i++) {
            int num = bigList.get(i);
            if (num % 2 == 0){
                smallList.add(num);
            }
        }
        return smallList;
    }
}