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1.创建Entity

/** * 完成Book的管理 * 要求：有包entity/dao/test→查询，修改，删除，增加操作(ArrayList来存储) * @author Administrator * */public class Books {	private String id;	private String name;	private double price;	public String getId() {		return id;	}	public void setId(String id) {		this.id = id;	}	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	public double getPrice() {		return price;	}	public void setPrice(double price) {		this.price = price;	}	@Override	public String toString() {		return "BooksEntity [id=" + id + ", name=" + name + ", price=" + price + "]";	}	public Books(String id, String name, double price) {		super();		this.id = id;		this.name = name;		this.price = price;	}		}

2.创建dao(方法）

import java.util.ArrayList;import java.util.Iterator;public class Booksdao {	//创建集合来存储Books	private ArrayList
   
     List = new ArrayList
    
     ();	//增	public boolean add(Books b) {		//判断b是否为空		if (b == null) {			//为空返回false			return false;		}		//否则add到List		List.add(b);		//返回true		return true;	}	//删	public boolean deleteById(String id) {		for (int i = 0; i < List.size(); i++) {			//集合中的元素赋值给b来存储			Books b = List.get(i);			if (id.equals(b.getId())) {				//判断值相等做删除				List.remove(i);				return true;			}		}return false;	}		public boolean updateBooks(Books s) {			for (int i = 0; i < List.size(); i++) {				//集合中的元素赋值给b来存储				Books b = List.get(i);				if (s.getId().equals(b.getId())) {					//将新对象s替换掉原本的b					List.set(i, s);					return true;				}			}return false;		}		/**	 * 	 * @param id 根据id找到对象	 * @return 如果为null则没有找到	 */	public Books getBooksById(String id) {		for (int i = 0; i < List.size(); i++) {			//集合中的元素赋值给b来存储			Books b = List.get(i);			if (id.equals(b.getId())) {				return b;			}		}return null;	}	//查询所有数据	public ArrayList
     
       getBooks(){		return List;	}}
     
    
   

3.测试

package com.cs.work01;import java.util.ArrayList;public class TestBooks {	public static void main(String[] args) {		Booksdao bd = new Booksdao();				//测试增，增加新对象		Books b1 = new Books("156484", "《百年孤独》", 34.40);		Books b2 = new Books("187916", "《美国大城市的生与死》", 9.9);		Books b3 = new Books("354891", "《城市发展史》", 24.90);		Books b4 = new Books("008763", "《理解》", 199);				bd.add(b1);		bd.add(b2);		bd.add(b3);		bd.add(b4);		//输出测试		ArrayList
   
     List = bd.getBooks();		if (List.isEmpty()) {			System.out.println("集合无数据");		}else			List.forEach(System.out::println);				//测试删除		System.out.println("*****************删除后*************");		bd.deleteById("008763");		if (List.isEmpty()) {			System.out.println("集合无数据");		}else			List.forEach(System.out::println);				//测试改		//id不变，修改name和price		System.out.println("*****************修改后*************");		Books b5 = new Books("354891", "《少年派克漂流记》", 79.8);		//返回修改结果flag		boolean flag = bd.updateBooks(b5);		System.out.println(flag);		//输出		if (List.isEmpty()) {			System.out.println("集合无数据");		}else			List.forEach(System.out::println);		//查		System.out.println("*****************查询结果*************");		System.out.println(bd.getBooksById("156484"));	}}
   

结果：

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