Collection接口和常用方法(以ArrayList为例)

以ArrayList，其他集合同理使用

基本使用方法

注：集合添加基本数据类型会自动装箱成对象

https://www.runoob.com/java/java-arraylist.html

遍历元素方式1(iterator)

https://www.runoob.com/java/java-iterator.html

遍历元素方式2(增强for)

增强for底层就是迭代器

https://www.runoob.com/java/collection-iterator.html

练习

1.创建3个Dog {name, age}对象，放入到 ArrayList 中，赋给List 引用
2.用迭代器和增强for循环两种方式来遍历
3.重写Dog的toString方法,输出name和age

package Collection;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
class Dog{
    private String name;
    private int age;

    public Dog(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;}

    @Override
    public String toString() {
        return "Dog{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}
public class Collection_ {
    @SuppressWarnings({"all"})//警告不提醒
    public static void main(String[] args) {
        List list = new ArrayList();
        list.add(new Dog("A",10));
        list.add(new Dog("B",6));
        list.add(new Dog("C",4));
        list.add(new Dog("D",11));

        System.out.println("1、使用迭代器遍历");
        Iterator it = list.iterator();
        while (it.hasNext()) {
            Object next =  it.next();
            System.out.println(next);
        }
        System.out.println("2、使用增强for遍历");
        for (Object obj:list){
            System.out.println(obj);
        }
    }
}