浅谈集合的应用

T和E可以是任何类型

class People{
    T age;//String
    E name;//int

    public T getAge() {
        return age;
    }

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

    public E getName() {
        return name;
    }

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

进行调用：
下面两种都行

People p=new People();
People p=new People();

        ArrayList a=new ArrayList();
        //等效方式：List list =new ArrayList();
        a.add("a");
		a.add("a");
		a.add("a");
        a.add("b");//向集合里增加元素
        List list =new CopyOnWriteArrayList();//写时复制
        a.set(2,"mama");//将集合里第二个元素替换为"mama"
        list.remove("a");//将特定的元素（"a"）删除
        //迭代器
        Iterator it=a.iterator();
        while(it.hasNext()){
            System.out.println(it.next());
        }

        //集合中的a.size相当于a.length
        for(int i=0;iSystem.out.println(c));

        Student s1 = new Student("小龙女", 23);
        Student s2 = new Student("任盈盈", 24);
        Student s3 = new Student("小龙女", 23);
        Student s4 = new Student("东方不败", 25);
        Student s5 = new Student("伊琳", 29);
        Student s6 = new Student("周芷若", 30);
        HashSet hashSet = new HashSet<>();
        hashSet.add(s1);
        hashSet.add(s2);
        hashSet.add(s3);
        hashSet.add(s4);
        hashSet.add(s5);
        hashSet.add(s6);//增加数据
        hashSet.remove("东方不败");//删除"东方不败"
        for (Student student : hashSet) {
            System.out.println(student.getName()+"=="+student.getAge());
        }
    }

  Map < String,Integer >map=new ConcurrentHashMap();
        map.put("bab",1);
        map.put("mam",2);//增加元素
        map.remove(1);//删除索引1指向的元素
        map.keySet().forEach(c->System.out.println(c));//只输出键
        map.values().forEach(c->System.out.println(c));//只输出值
        map.entrySet().forEach(c->System.out.println(c));//都输出