List集合-Arraylist

Arraylist

创建集合

package eight.list.arraylist;

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

public class Student {
    public static void main(String[] args) {
        //创建集合
        //List aa = new ArrayList();
        ArrayList aa = new ArrayList();
        aa.add("a");
        aa.add(123);
        aa.add(true);
        System.out.println(aa);
        //System.out.println(aa.toString());//打印对象的引用会默认调用tostring方法
    }
}
真题练习

package eight.list.arraylist;

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

public class Test {
    public static void main(String[] args) {
        Dog d1 = new Dog("花花","中华田园犬");
        Dog d2 = new Dog("龙龙","泰迪");
        Dog d3 = new Dog("壮壮","哈士奇");
        Dog d4 = new Dog("迪迪","拉布拉多");
        ArrayList list = new ArrayList();
        list.add(d1);
        list.add(d2);
        list.add(d3);
        list.add(d4);
        System.out.println(list);
        System.out.println(list.size());//size方法，打印集合元素个数

        //删除指定狗狗
        for (int i = 0; i < list.size(); i++) {
            if (list.contains(d1)){//contains是否包含
                list.remove(i);//remove删除
                break;
            }else{
                System.out.println("没有指定狗狗");
            }

        }
        System.out.println(list);
}}

package eight.list.arraylist;

public class Dog {
    private String name;
    private String trye;



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

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

    public String getName() {
        return name;
    }

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

    public String getTrye() {
        return trye;
    }

    public void setTrye(String trye) {
        this.trye = trye;
    }
    public void eat(){}
    public  void run(){}

}

泛型集合 在编译时增加类型检查

package eight.list.arraylist;
//泛型集合  在编译时增加类型检查
import java.util.ArrayList;
import java.util.List;

public class GenericTest {
    public static void main(String[] args) {
        ArrayList<String> list = new ArrayList<String>();//加泛型把错误提到编译期
        list.add("qqyumidi");
        list.add("corn");
        //list.add(100);//Integer类型转换异常

        for (int i = 0; i < list.size(); i++) {
            //Object o1 = list.get();
           String object = (String) list.get(i);//Object转换String
           System.out.println(object);
            //System.out.println(list.get(i));

        }
    }
}