【Java入门杂记】【七】

• • 继承
  • • 集合
    • • 泛型集合--ArrayList
      • 泛型集合--HashMap
  • 分层
  • • 学生信息管理系统
    • • Page
      • StudentService
      • StudentDao
      • Student
      • Test

“高级版的数组”
不同于数组，长度是动态可变的
集合的框架：

创建集合对象：

ArrayList<值的类型> list = new ArrayList<值的类型>（）；

获取集合长度：

list.size();

添加集合元素：

list.add(对象或值);

获取集合元素：

list.get(下标);

修改/替换集合元素：

list set(下标，对象或值)；

循环集合元素：

for
foreach

删除集合元素：

list.remove(下标);        //通过下标删除指定元素
list.remove(对象名)；        //通过对象名删除指定元素
list.cleat();
//删除时自动补上，序号连续

package test01;

import java.util.ArrayList;

public class Test {
	public static void main(String[] args) {
		
		ArrayList list = new ArrayList();
		
		System.out.println(list.size());		
		
		list.add("111");
		list.add("222");
		list.add("444");
		//查看长度
		System.out.println(list.size());
		
		//获取操作
		System.out.println(list.get(1));    
		
		//替换操作
		list.set(1, "333");
		
		//循环输出
		System.out.println("循环输出");
		for(int i = 0;i < list.size();i++) {
			System.out.println(list.get(i));
		}
		
		//增强for
		System.out.println("增强for");
		for (String str : list) {
			System.out.println(str);
		}
		
		//删除操作
		System.out.println("删除操作↓");
		list.remove(0);
		list.remove("333");
		list.clear();
		for(int i = 0;i < list.size();i++) {
			System.out.println(list.get(i));
		}
		
	}
}

也称“键值集合”
key–value
创建集合对象

HashMap map = new HashMap();

获取集合长度

map.size();

添加集合对象

map.put(key,value);

获取集合元素

map.get(key);

循环集合元素

foreach  //对键的循环
map.keySet();
foreach  //对值的循环
map.values();

删除集合元素

map.remove(key);
map.clear();

package test02;

import java.util.HashMap;

public class Test {
	public static void main(String[] args) {
		HashMap map = new HashMap();
		
		//添加元素
		map.put("a", "alice");
		map.put("t", "tony");
		map.put("j", "jhon");

		//替换元素
		map.put("a", "victory");
		
		//获取长度
		System.out.println(map.size());
		
		//通过键获取值
		System.out.println(map.get("a"));
		
		//增强foreach获取键值
		for (String key : map.keySet()) {
			System.out.println(key);
		}
		
		//增强foreach获取值
		for (String value : map.values()) {
			System.out.println(value);
		}
		
		//删除操作（通过键删除）
		map.remove("a");
//		map.clear();
		for (String value : map.values()) {
			System.out.println(value);
		}
	}
}

表示层
业务逻辑层（Business Logic Layer）
数据访问层（Data Access Layer）

使用Package进行分层

表示层：page等
业务逻辑层：service
数据访问层：dao（Data Access Object）

package page;

import java.util.ArrayList;
import java.util.Scanner;

import entity.Student;
import service.StudentService;

public class Page {

	StudentService ss = new StudentService();
	Scanner input = new Scanner(System.in);
	
	public void init() {
		ss.init();
		HomePage();
	}
	
	public void HomePage() {
		while(true) {
			System.out.println("*********************");
			System.out.println("1.查询");
			System.out.println("2.添加");
			System.out.println("3.修改");
			System.out.println("4.删除");
			System.out.println("5.退出");
			System.out.println("*********************");
			System.out.println("请选择：");
			
			int choice = input.nextInt();
			if(choice == 1) {
				searchPage();
			}else if(choice == 2) {
				addPage();
			}else if(choice == 3) {
				updatePage();
			}else if(choice == 4) {
				updatePage();
			}else if(choice == 5) {
				System.out.println("谢谢使用");
				break;
			}else {
				System.out.println("输入错误，重新输入");
			}
		}
	}
	
	public void searchPage() {
		ArrayList list = ss.search();
		
		System.out.println("*************************");
		System.out.println("编号t姓名t年龄t爱好");
		System.out.println("*************************");
		for (Student s : list) {
			System.out.print(s.getId() + "t");
			System.out.print(s.getName() + "t");
			System.out.print(s.getAge() + "t");
			System.out.print(s.getHobby() + "n");
		}
		System.out.println("*************************");	
	}
	
	public void addPage() {
		System.out.println("请输入编号");
		int id = input.nextInt();
		
		System.out.println("请输入姓名");
		String name = input.next();
		
		System.out.println("请输入年龄");
		int age = input.nextInt();
		
		System.out.println("请输入爱好");
		String hobby = input.next();
		
		Student stu = new Student(id,name,age,hobby);
		int result = ss.add(stu);
		if(result == 1) {
			System.out.println("添加成功");
		}else {
			System.out.println("添加失败");
		}
		
	}
	
	public void updatePage() {
		System.out.println("请输入编号");
		int id = input.nextInt();
		
		System.out.println("请输入姓名");
		String name = input.next();
		
		System.out.println("请输入年龄");
		int age = input.nextInt();
		
		System.out.println("请输入爱好");
		String hobby = input.next();
		
		Student stu = new Student(id,name,age,hobby);
		int result = ss.update(stu);
		if(result == 1) {
			System.out.println("修改成功");
		}else {
			System.out.println("修改失败");
		}
		
	}
	
	public void deletePage() {
		System.out.println("请输入要删除的编号");
		int id = input.nextInt();
		
		int result = ss.delete(id);
		if(result == 1) {
			System.out.println("删除成功");
		}else {
			System.out.println("删除失败");
		}
		
	}
	
}

package service;

import java.util.ArrayList;

import dao.StudentDao;
import entity.Student;

public class StudentService {
	
	StudentDao sd = new StudentDao();

	public void init() {
		sd.init();
	}
	
	public ArrayList search(){
		return sd.search();
	}
	
	public int add(Student stu) {
		return sd.add(stu);
	}
	
	public int update(Student stu) {
		return sd.update(stu);
	}
	
	public int delete(int id) {
		return sd.delete(id);
	}
	
}

package dao;

import java.util.ArrayList;

import entity.Student;

public class StudentDao {
	ArrayList list = new ArrayList();
	
	//1.信息初始化
	public void init() {
		Student stu1 = new Student(1001,"alice",19,"play");
		Student stu2 = new Student(1002,"tony",20,"baseball");
		Student stu3 = new Student(1003,"victor",21,"basketball");
		
		list.add(stu1);
		list.add(stu2);
		list.add(stu3);
		
	}
	
	//2.获取Student的值
	public ArrayList search() {
		return list;
	}
	
	//3.添加信息
	public int add(Student stu) {
		boolean flag = false;
		for (Student s : list) {
			if(s.getId() == stu.getId()) {
				flag = true;
			}
		}
		if(flag == true) {
			return 0;
		}else {
			list.add(stu);
			return 1;
		}

	}
	
	//4.修改信息
	public int update(Student stu) {
		boolean flag = false;
		int index = 0;
		
		for (int i = 0; i < list.size(); i++) {
			if(list.get(i).getId() == stu.getId()) {
				flag = true;
				index = i;
			}
		}
		
		if(flag == true) {
			list.set(index, stu);
			return 1;
		}else {
			return 0;
		}
	
	}
	
	//5.删除信息
	public int delete(int id) {
		boolean flag = false;
		int index = 0;
		
		for (int i = 0; i < list.size(); i++) {
			if(list.get(i).getId() == id) {
				flag = true;
				index = i;
			}
		}
		
		if(flag == true) {
			list.remove(index);
			return 1;
		}else {
			return 0;
		}
	}	
	
}

package entity;

public class Student {
	private int id;
	private String name;
	private int age;
	private String hobby;
	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 getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public String getHobby() {
		return hobby;
	}
	public void setHobby(String hobby) {
		this.hobby = hobby;
	}
	public Student() {
		super();
	}
	public Student(int id, String name, int age, String hobby) {
		super();
		this.id = id;
		this.name = name;
		this.age = age;
		this.hobby = hobby;
	}
}

package test;

import page.Page;

public class Test {
	public static void main(String[] args) {
		Page page = new Page();
		page.init();
	}
}