JAVA学习笔记33——模拟实现HandSet+数据存储综合练习（javabean版+容器板）

最近在看JAVA教学的视频，觉得老师讲的很好，同时借用源代码还有笔记来撰写本系列博客，记录自己的学习内容，同时也供看到的人学习。

本篇第一个内容是模拟实现HandSet，其实这个模拟和之前的相比简陋了很多，因为Set的源码是比较复杂的，而且Set很大一部分是依赖于Map的，所以模拟的代码量并不多：

import java.util.HashMap;/** * 自定义自己的HashSet，Set里面存放的相当于Map里面的key值，而真正的value则放在Map里面 */public class SxtHashSet {HashMap map; //用来存放真实的元素信息private static final Object PRESENT = new Object();public SxtHashSet(){map = new HashMap();  //参考源码}public int size(){return map.size();}public void add(Object o){map.put(o, PRESENT);   //set的不可重复就是利用了map里面键对象的不可重复！}public static void main(String[] args) {SxtHashSet s = new SxtHashSet();s.add("aaa");s.add(new String("aaa"));System.out.println(s.size());}}

接下来进行的是一个小练习，利用所学知识进行一个数据存储的练习，设计的数据表格如下：

两种解决方式，第一种是用javabean（一种常见的数据存储容器，利用构造器来进行数据导入与存储，JSP开发里面经常用到）：

import java.text.DateFormat;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Date;public class Employee {   //这种类有时称为JavaBean，也称为实体类private int id;private String name;private int salary;private String department;private Date hireDate;//利用Eclipse自动添加构造器“Generate Constructor using Fields”选项public Employee(int id, String name, int salary, String department,String hireDate) {super();this.id = id;this.name = name;this.salary = salary;this.department = department;DateFormat format = new SimpleDateFormat("yyyy-MM");try {this.hireDate = format.parse(hireDate);} catch (ParseException e) {e.printStackTrace();}}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getSalary() {return salary;}public void setSalary(int salary) {this.salary = salary;}public String getDepartment() {return department;}public void setDepartment(String department) {this.department = department;}public Date getHireDate() {return hireDate;}public void setHireDate(Date hireDate) {this.hireDate = hireDate;}}

import java.awt.print.Printable;import java.text.DateFormat;import java.text.SimpleDateFormat;import java.util.ArrayList;import java.util.Date;import java.util.List;public class Test01 {  //用JavaBean的方法来进行数据存储public static void main(String[] args) {//加上合适的构造器之后，一行对应一条记录Employee e = new Employee(0301,"gaoqi",3000,"xiangmubu","2007-10");Employee e2 = new Employee(0302,"mashibing",3000,"jiaoxuebu","2006-10");Employee e3 = new Employee(0303,"peixin",3000,"jiaoxuebu","2007-10");List<Employee> list = new ArrayList<Employee>();   //使用泛型list.add(e);list.add(e2);list.add(e3);printEmpName(list);}public static void printEmpName(List<Employee> list){for(int i=0;i<list.size();i++){System.out.println(list.get(i).getName());}}}

第二种就是用刚学过的Map容器来存储：

import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;public class Test02 {   //用容器来存储public static void main(String[] args) {     //一行记录用一个map来封装Map map = new HashMap();map.put("id", 0301);map.put("name", "gaoqi");map.put("salary", 3050);map.put("department", "xiangmubu");map.put("hireDate", "2007-10");Map map2 = new HashMap();map2.put("id", 0302);map2.put("name", "mashibing");map2.put("salary", 3050);map2.put("department", "xiangmubu");map2.put("hireDate", "2007-10");Map map3 = new HashMap();map3.put("id", 0303);map3.put("name", "peixin");map3.put("salary", 3050);map3.put("department", "xiangmubu");map3.put("hireDate", "2007-10");List<Map> list = new ArrayList<Map>();list.add(map);list.add(map2);list.add(map3);printEmpName(list);}public static void printEmpName(List<Map> list){for(int i=0;i<list.size();i++){Map tempMap = list.get(i);System.out.println(tempMap.get("name"));}}}