Java面向对象基础
构造器
public class Car {
String name;
double price;
/**
无参数构造器(默认存在的)
*/
public Car(){
System.out.println("无参数构造器被触发执行~~~");
}
/**
有参数构造器
*/
public Car(String n, double p){
System.out.println("有参数构造器被触发执行~~~");
name = n;
price = p;
}
}
this指向
public class Car {
String name;
double price;
public void goWith(String name){
System.out.println(this.name +"正在和：" + name +"比赛！");
}
/**
无参数构造器(默认存在的)
*/
public Car(){
System.out.println("无参数构造器被触发执行~~~");
}
/**
有参数构造器
*/
public Car(String name, double price){
System.out.println("有参数构造器被触发执行~~~");
System.out.println(this);
this.name = name;
this.price = price;
}
}
面向对象基础：JavaBean
可以定义完成员变量右键Generate Get Set 自动生成函数
public class User {
private double height;
private String name;
private double salary;
private String address;
private String phone;
public User() {
}
public User(double height, String name, double salary, String address, String phone) {
this.height = height;
this.name = name;
this.salary = salary;
this.address = address;
this.phone = phone;
}
public double getHeight() {
return height;
}
public void setHeight(double height) {
this.height = height;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
}
购物车练习
定义类 Goods.java
package com.domain.demo;
public class Goods {
// javabean要全部私有
private int id;
private String name;
private double price;
private int buyNumber;
public Goods(){
}
// IDE右键Generate Constructor 一般有参数的构造器不常用
public Goods(int id, String name, double price, int buyNumber) {
this.id = id;
this.name = name;
this.price = price;
this.buyNumber = buyNumber;
}
// IDE右键Generate Getter Setter 自动生成
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 double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public int getBuyNumber() {
return buyNumber;
}
public void setBuyNumber(int buyNumber) {
this.buyNumber = buyNumber;
}
}
ShopCarTest.java
package com.domain.demo;
import java.util.Scanner;
public class ShopCarTest {
public static void main(String[] args) {
Goods[] shopCar = new Goods[100]; // [null, null, ...]
// 选中代码 Ctrl + Alt + T 可以加 while
while (true) {
System.out.println("请您选择如下命令操作：");
System.out.println("添加到购物车 add");
System.out.println("查询商品 query");
System.out.println("修改商品购买数量 update");
System.out.println("结算购物车金额 pay");
Scanner sc = new Scanner(System.in);
System.out.println("请您输入命令：");
String command = sc.next();
switch (command){
case "add":
// 添加到购物车
// Alt + 回车 自动创建方法
addGoods(shopCar, sc);
break;
case "query":
// 查询商品
queryGoods(shopCar);
break;
case "update":
// 修改商品购买数量
updateGoods(shopCar, sc);
break;
case "pay":
// 结算购物车金额
pay(shopCar);
break;
default:
System.out.println("没有该功能");
}
}
}
public static void pay(Goods[] shopCar) {
queryGoods(shopCar);
double money = 0;
// [g1, g2, null, ...]
for (int i = 0; i < shopCar.length; i++) {
Goods g = shopCar[i];
if(g != null) {
money += g.getPrice() * g.getBuyNumber();
} else {
break;
}
}
System.out.println("订单总金额："+ money);
}
public static Goods getGoodsById(Goods[] shopCar,int id) {
// shopCar = [g1, g2, g3, null, null, null, ...]
for (int i = 0; i < shopCar.length; i++) {
Goods g = shopCar[i];
if(g != null) {
//判断商品id是不是查找的
if(g.getId() == id) {
return g;
}
} else {
// 遍历到最后都没找到
return null;
}
}
// 假设100个商品都存在并且找完了100个商品都没有找到
return null;
}
public static void updateGoods(Goods[] shopCar, Scanner sc) {
// 根据用户输入ID修改对应商品
while (true) {
System.out.println("请输入要修改的商品ID");
int id = sc.nextInt();
Goods g = getGoodsById(shopCar, id);
if(g == null) {
// 没有该商品
System.out.println("没有找到该商品");
} else {
// 存在该商品对象，可以进行修改
System.out.println("请输入" + g.getName() + "商品最新购买数量");
int buyNumber = sc.nextInt();
g.setBuyNumber(buyNumber);
System.out.println("修改完成");
queryGoods(shopCar);
break;
}
}
}
public static void queryGoods(Goods[] shopCar) {
System.out.println("==========查询购物车信息如下==========");
System.out.println("编号\t\t名称\t\t价格\t\t购买数量");
for (int i = 0; i < shopCar.length; i++) {
Goods g = shopCar[i];
if (g != null) {
System.out.println(g.getId() + "\t\t" + g.getName() + "\t\t" + g.getPrice() + "\t\t" + g.getBuyNumber());
} else {
// 遍历结束
break;
}
}
}
public static void addGoods(Goods[] shopCar, Scanner sc) {
System.out.println("请您输入购买商品编号（不重复）");
int id = sc.nextInt();
System.out.println("输入商品名称");
String name = sc.next();
System.out.println("输入商品数量");
int buyNumber = sc.nextInt();
System.out.println("输入购买的价格");
double price = sc.nextDouble();
Goods g = new Goods();
g.setId(id);
g.setName(name);
g.setBuyNumber(buyNumber);
g.setPrice(price);
// Goods push in array
// shopCar = [a, a2, numm, .....]
for (int i = 0; i < shopCar.length; i++) {
// 寻找位置
if(shopCar[i] == null){
// 说明此位置没有元素存入
shopCar[i] = g;
// 结束，商品成功存入，不需要再找位置了
break;
}
System.out.println("您的商品" + g.getName() + "已经添加到购物车");
}
}
}