2019.2.22集合框架

package com.student;

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;

public class TestStudents {
    public static void main(String[] args) {
        Map<String,Student> stu = new HashMap<String,Student>();
        Student s1 = new Student("张三","男");
        Student s2 = new Student("李四","男");
        Student s3 = new Student("王五","女");
        //添加键值对
        stu.put("jack", s1);
        stu.put("tom", s2);
        stu.put("lisa", s3);
        
        
        //获得jack所对应的值
        Student s = stu.get("jack");
        System.out.println(s.getName());
        System.out.println(s.getSex());
        System.out.println("***********************");
        //使用键的集合set遍历键值信息
        Set<String> set = stu.keySet();
        for(String s11 : set) {
            Student stus = stu.get(s11);
            System.out.println(stus.getName()+stus.getSex());
        }
        
        //使用值得集合coll遍历键值信息
        System.out.println("************************");
        Collection<Student> coll = stu.values();
        for(Student st : coll) {
            System.out.println(st.getSex()+st.getName());
        }
        
        
        System.out.println("************************");
        System.out.println("请输入要查找的学生英文名：");
        Scanner sc = new Scanner(System.in);
        String key = sc.next();
        if(stu.containsKey(key)) {
            Student st = stu.get(key);
            System.out.println("要查找的学生是："+st.getName()+"-"+st.getSex());
        }else {
            System.out.println("没有要查找的学生信息！");
        }
        
    }

}

输出：

collection无序不唯一

List有序不唯一

Set无序唯一

 

ArrayList实现了长度可变的数组，遍历元素和随机访问元素的效率比较高

LinkedList采用链表存储方式，插入，删除元素时效率比较高