key Value

public class Dog {
    private int id;
    private String name;

    @Override
    public String toString() {
        return "Dog{" +
                "id=" + id +
                ", name=‘" + name + ‘\‘‘ +
                ‘}‘;
    }

    public Dog() {
    }

    public Dog(int id, String name) {
        this.id = id;
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public static void main(String[] args) {
        Dog dog = new Dog();
        System.out.println(dog);
    }
}

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


public class ArrayListTest {
    public static void main(String[] args) {

        ArrayList arrayList = new ArrayList();
        arrayList.add(1);
        arrayList.add(1);
        arrayList.add(1);
        arrayList.add(1);
        arrayList.add(1);
        System.out.println("arrayList.size() = " + arrayList.size());
        System.out.println("arrayList.iterator() = " + arrayList.iterator());

        List list = new ArrayList();
        Dog dog1 = new Dog(1, "wang1");
        Dog dog2 = new Dog(2, "wang2");
        Dog dog3 = new Dog(3, "wang3");
        Dog dog4 = new Dog(4, "wang4");
        Dog dog5 = new Dog(5, "wang5");
        list.add(dog1);
        list.add(dog2);
        list.add(dog3);
        list.add(dog4);
        list.add(dog5);

        System.out.println("list.size() = " + list.size());

        System.out.println("list.get(3) = " + list.get(2));

        System.out.println("list.remove(5) = " + list.remove(3));

        System.out.println("list.contains(wang2) = " + list.contains(dog2));

        list.add(0, new Dog(6, "wang6"));

        list.add(1, new Dog(9, "wang9"));

        for (int i = 0; i < list.size(); i++) {
            Dog dog = (Dog) list.get(i);
            System.out.println("dog.getName() = " + dog.getName());
        }
        System.out.println("*****************我是华丽的分界线*********************");
        Object[] array = list.toArray();
        for (int i = 0; i < array.length; i++) {
            Dog dog = (Dog) array[i];
            System.out.println("dog.getName() = " + dog.getName());
        }
        System.out.println("*****************我是华丽的分界线*********************");
        for (Object a : list) {
            Dog dog = (Dog) a;
            System.out.println("dog.getName() = " + dog.getName());
        }
        System.out.println("*****************我是华丽的分界线*********************");
        Iterator iterator = list.iterator();
        while (iterator.hasNext()) {
            Dog next = (Dog) iterator.next();
            System.out.println("next.getName() = " + next.getName());
        }
        System.out.println("*****************我是华丽的分界线*********************");
        list.clear();//清空整个集合=。= 一般人我不告诉他 到时候清空了 还怪我 (ˉ▽￣～) 切~~
        System.out.println("*****************我是华丽的分界线*********************");
        System.out.println("list.isEmpty() = " + list.isEmpty());
        System.out.println("list.size() = " + list.size());

    }
}