文章标题

目录

集合
泛型
JDK下载

集合的使用

ArrayList的使用

ArrayList<Student> students = new ArrayList<Student>();        students.add(new Student("李华", 20));        students.add(new Student("小明", 25));        students.add(new Student("King",18));        for(Student s:students){            System.out.println(s.getName()+s.getAge());        }

Hashset的使用

HashSet<Student> set = new HashSet<Student>();        Student set1 = new Student("set1", 1);        Student set2 = new Student("set2", 2);        Student set3 = new Student("set3", 3);        set.add(set1);        set.add(set2);        set.add(set3);        Iterator<Student> iterator = set.iterator();//元素迭代器        while (iterator.hasNext()) {            System.out.println(iterator.next().getName());        }

HashMap的使用

HashMap<String,String> countries = new HashMap<String,String>();        countries.put("Cn","中国");        countries.put("USA","美国");        countries.put("UK","英国");        System.out.println(countries.get("Cn"));

泛型的使用

泛型

Student<Dog> lihua = new Student<Dog>("李华", 20);        Dog huang = new Dog();        lihua.setPets(huang);        lihua.getPets();        Student<Cat> xiaoming = new Student<Cat>("小明", 25);        Cat tom = new Cat();        xiaoming.setPets(tom);        xiaoming.getPets();//      若<T extends Animal>E_pet未继承,则会出现错误//      Student<E_pet> king = new Student<E_pet>("King", 18);//      E_pet mouse = new E_pet();//      king.setPets(mouse);//      king.getPets();