集合-HashMap

1)
Map list = new HashMap();
        list.put("Isaac", "王远航");
        list.put("Jay", "周杰伦");
        list.put("Akon", "阿肯");
        //Object obj=list.values();
        System.out.println("输入你要找的姓名");
        String name = input.next();
        //Object obj=null;
        boolean flag=false;
        String name1=null;
        for(Object obj:list.values()) {
            if(obj.equals(name)) {
                flag=true;
                name1=(String)obj;
                break;
            }
        }
        if(flag==true) {
            System.out.println(name1);
        }else {
            System.out.println("没找到");
        }

1:list.values()集合也可以通过加强for依次将值赋给Object对象

2）ste keySet()的返回值为set类型  是无序唯一的

collection values()返回值类型为collection类型   是无序不唯一的

3）
public class Iterator {
    public static void main(String[] args) {
        
        Map list = new HashMap();
        list.put("Isaac", "王远航");
        list.put("Jay", "周杰伦");
        list.put("Akon", "阿肯");
        
        //方法1：依次取出键值对
        //Set name2 = list.keySet();可以先拿到key的集合 然后用name2去依次赋值遍历 
        for(Object obj:list.keySet()) {
            String name1=(String)obj;
            System.out.println(name1+" "+list.get(name1));
            //因为list.get(name1)的返回值类型为collect类型所以可以强成String类型
        }
        //方法2使用Iterator迭代器
        Iterator itt = list.iterator();
        while(itt.hasNext()) {
            String names = (String)itt.next();
            String value = (String)list.get(names);
            System.out.println(names+" "+value);
            }
        //方法3先拿到Map中的键值对，然后在每对键值对中分别取出键和值
        Set ms = list.entrySet();
        for(Object obj : ms) {
            Map.Entry me =(Map.Entry)obj;
            Object key = me.getKey();
            Object value = me.getValue();
            System.out.println((String)key+(String)value);
        }
    }
    }

3：三种方式获得 每个键值对 的对应键和值

4）
public static void main(String[] args) {
        Ldemo2 title1 = new Ldemo2("张三",'男');
        Ldemo2 title2 = new Ldemo2("李四",'男');
        Ldemo2 title3 = new Ldemo2("王五",'女');
        //Ldemo2 title = new Ldemo2("","");
        Map<String, Ldemo2> list = new HashMap<String, Ldemo2>();
        list.put("Isaac",title1);
        list.put("Jay",title2);
        list.put("Akon",title3);
        
        
        
        for(String obj:list.keySet()) {
            //String name1=(String)obj;
            System.out.println(obj+" "+list.get(obj).getNames());
            
        }

4：list.get(obj).getNames()可以这样写 得到name的值

5)
Set<Map.Entry<String, String>> ms=list.entrySet();
        for(Map.Entry<String, String> obk:ms) {
            System.out.print(obk.getKey()+""+obk.getValue());
        }

5:使用泛型获得键值对

6）
public class TextStudent {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        Student title1 = new Student("黎明", '男');
        Student title2 = new Student("周杰伦", '男');
        Student title3 = new Student("碧昂斯", '女');
        Student title4 = new Student("艾薇儿", '女');
        Map<String, Student> list = new HashMap<String, Student>();
        //也可以直接这么写list.put("1", new Student("艾薇儿", '女'));
        list.put("1", title1);
        list.put("2", title2);
        list.put("3", title3);
        list.put("4", title4);
        System.out.println("请输入你要找的学员编号");
        String number = input.next();
        /*boolean flag = false;
        // String search;
        for (String search : list.keySet()) {
            if (number.equals(search)) {

                flag = true;
                break;
            }
        }
        if (flag==true) {
            Student title = list.get(number);
            System.out.println("找到学员：" + title.getNames() + " " + title.getSex());
        } else {
            System.out.println("没找到相关学员");
        }*/
        if(list.containsKey(number)) {//没用泛型
            Student stu = (Student)list.get(number);
            System.out.println("找到学员：" + stu.getNames() + " " + stu.getSex());
        }else {
            System.out.println("没有您要找的学员");
        }
    
    
    }

}

6：通过键寻找值