• 集合


    集 合

    一、 Collectiong

    1、   list:有序集合,数据可重复;

    (1)、ArryList:动态数组。

    特点:数组的存储结构空间连续;

    运行逻辑:每次操作时,都要改变数组的大小。(添加、移除操作时,会新建数组,然后将数组内容复制到新建数组中,增加了时间、空间的复杂度),但是读取、查询的效率高;

    新增:add(“黎明”);

    插入:add(2,“黎明”);

    移除:remove(2);

    例题:
        ArrayList<String> sp = new ArrayList<String>();
            
            System.out.println("=========手机卖场========");
            
            System.out.println("----------增加-----------");
            sp.add("oppo手机");
            sp.add("vivo手机");
            sp.add("苹果手机");
            sp.add("金立手机");
            sp.add("魅族手机");
            
            for (int i = 0; i < sp.size(); i++) {
                System.out.println(sp.get(i));
            }
            
            System.out.println("----------插入------------");
            sp.add(3, "小米手机");
            for (int i = 0; i < sp.size(); i++) {
                System.out.println(sp.get(i));
            }
            
            System.out.println("----------修改------------");
            sp.remove(4);
            sp.add(4, "华为手机");
            
            for (int i = 0; i < sp.size(); i++) {
                System.out.println(sp.get(i));
            }
            
            System.out.println("----------删除------------");
            sp.remove(3);
            for (int i = 0; i < sp.size(); i++) {
                System.out.println(sp.get(i));
            }

    (2)、LinkedList:链表结构;

    对内存空间没有特殊要求;

    运行逻辑:

    新增:将尾元素连接到新增元素,新增元素作为新的尾元素;

    插入:找到指定位置的元素新增元素,将指定元素前一个连接到新的元素上,而新的元素连接到指定元素;

    移除:找到指定元素,将指定元素连接到下一个元素;

    缺点:不适合数据的查找读取;

    addFrist();增加头部;

    addLast();增加尾部;

    removeFirst();删除头部;

    removeLast();删除尾部;

    例题:
            LinkedList<String> sp = new LinkedList<String>();
            
            System.out.println("=========动物园========");
            
            System.out.println("----------增加-----------");
            sp.add("熊猫");
            sp.add("老虎");
            sp.add("狮子");
            sp.add("大象");
            sp.add("");
            
            for (int i = 0; i < sp.size(); i++) {
                System.out.println(sp.get(i));
            }
            
            System.out.println("----------插入------------");
            sp.add(3, "豹子");
            for (int i = 0; i < sp.size(); i++) {
                System.out.println(sp.get(i));
            }
            
            System.out.println("----------修改------------");
            sp.remove(4);
            sp.add(4, "斑马");
            
            for (int i = 0; i < sp.size(); i++) {
                System.out.println(sp.get(i));
            }
            
            System.out.println("----------删除------------");
            sp.remove(3);
            for (int i = 0; i < sp.size(); i++) {
                System.out.println(sp.get(i));
            }
            
            System.out.println("----------增加头部与尾部---------");
            sp.addFirst("泰迪");
            sp.addLast("蟒蛇");
            for (int i = 0; i < sp.size(); i++) {
                System.out.println(sp.get(i));
            }
            
            System.out.println("----------删除头部与尾部-----------");
            sp.removeFirst();
            sp.removeLast();
            for (int i = 0; i < sp.size(); i++) {
                System.out.println(sp.get(i));
            }            

    2、   set:无序,数据不可重复;

    添加重复数据覆盖原有的数据;

    例题:
           HashSet<String> ha = new HashSet<String>();
    
          
    
           System.out.println("===========4S旗舰店=======");
    
          
    
           System.out.println("===========添加===========");
    
           ha.add("宝马");
    
           ha.add("法拉利");
    
           ha.add("奥迪");
    
           ha.add("捷豹");
    
           ha.add("宝马");
    
           //Iterator是叠带器;读取数据
    
           Iterator<String> it = ha.iterator();
    
           while(it.hasNext()){
    
               String s = it.next();
    
               System.out.println(s);
    
           }
    
           System.out.println("===========删除===========");
    
           ha.remove("宝马");
    
           Iterator<String> te = ha.iterator();
    
           while(te.hasNext()){
    
               String s1 = te.next();
    
               System.out.println(s1);
    
           }    

    二、 Map:k、v模式集合;

    K—>key(键);具有唯一性;

    V—>value(值);

    类中:

    例题:
    类中:
    
        private String worknum;
    
        private String workname;
    
        private String phone;
    
        public Work(String worknum, String workname, String phone) {
    
           super();
    
           this.worknum = worknum;
    
           this.workname = workname;
    
           this.phone = phone;
    
        }
    
        public String getWorknum() {
    
           return worknum;
    
        }
    
        public void setWorknum(String worknum) {
    
           this.worknum = worknum;
    
        }
    
        public String getWorkname() {
    
           return workname;
    
        }
    
        public void setWorkname(String workname) {
    
           this.workname = workname;
    
        }
    
        public String getPhone() {
    
           return phone;
    
        }
    
        public void setPhone(String phone) {
    
           this.phone = phone;
    
    }

    程序入口:

        Work person1 = new Work("13112", "黎明", "18354202161");
    
           Work person2 = new Work("13113", "炜婷", "12394358945");
    
           Work person3 = new Work("13114", "雅婧", "15847589494");
    
           Work person4 = new Work("13115", "小明", "14855840044");
    
           HashMap<String, Work> ha = new HashMap<String,Work>();
    
           //增加数据;person1.getWorknum()是键,person1是值;
    
           ha.put(person1.getWorknum(), person1);
    
           ha.put(person2.getWorknum(), person2);
    
           ha.put(person3.getWorknum(), person3);
    
           ha.put(person4.getWorknum(), person4);
    
          
        //键盘输入;
           Scanner input = new Scanner(System.in);
    
           System.out.println("请输入一个员工工号:");
    
           String st = input.next();
    
           //get(键);获取数据
    
           Work person = ha.get(st);
    
           System.out.println("员工是:"+person.getWorkname());
    
          
    
           System.out.println("====================================");
    
          
    
           //根据map集合中的keyset()遍历value();
    
           Set<String> keyset = ha.keySet();
    
           //显示数据,固定格式;
    
           Iterator<String> it1 = keyset.iterator();
    
           while(it1.hasNext()){
    
               String key = it1.next();
    
               Work persons1 = ha.get(key);
    
               System.out.println("员工是:"+persons1.getWorkname());
    
           }
    
          
    
           System.out.println("=====================================");
    
          
    
           //根据map集合中的value()遍历value();
    
           Collection<Work> coll_work = ha.values();
    
           Iterator<Work> it2 = coll_work.iterator();
    
           while(it2.hasNext()){
    
               Work persons2 = it2.next();
    
               System.out.println("员工是:"+persons2.getWorknum());
    
         }
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  • 原文地址:https://www.cnblogs.com/liming027/p/6511909.html
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