“商苑面馆 :Java知识串讲”的版本间的差异
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(→任务三 JAVA面向对象程序编程(一)) |
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第440行: | 第440行: | ||
return true; | return true; | ||
} | } | ||
+ | |||
+ | public String toString(){ | ||
+ | return "名称:" +this.name+"价格:"+ | ||
+ | this.price + "数量: " + this.num; | ||
+ | } | ||
+ | |||
public static void main(String[] args) { | public static void main(String[] args) { | ||
// TODO Auto-generated method stub | // TODO Auto-generated method stub | ||
第457行: | 第463行: | ||
System.out.println("数量"+ n2.getNum()); | System.out.println("数量"+ n2.getNum()); | ||
+ | } | ||
+ | |||
+ | } | ||
+ | </nowiki> | ||
+ | |||
+ | ==任务四 对象数组== | ||
+ | |||
+ | <nowiki>package test2; | ||
+ | |||
+ | public class Test { | ||
+ | |||
+ | public static void main(String[] args) { | ||
+ | // TODO Auto-generated method stub | ||
+ | Noodle [] nl = new Noodle[3]; | ||
+ | nl[0] = new Noodle("炸酱面",12.0,3); | ||
+ | nl[1] = new Noodle("臊子面",14.0,2); | ||
+ | nl[2] = new Noodle("刀削面",10.0,5); | ||
+ | |||
+ | for(int i=0;i<3;i++){ | ||
+ | if(nl[i].getName().equals("臊子面")){ | ||
+ | System.out.println(nl[i].toString()); | ||
+ | } | ||
+ | |||
+ | } | ||
} | } | ||
} | } | ||
</nowiki> | </nowiki> |
2019年3月27日 (三) 02:13的版本
任务二 JAVA程序开发基础
2.1变量和表达式
2.2智能决策:选择结构
三目运算符
package demo1; import java.util.Scanner; public class happy08 { public static void main(String[] args) { // TODO Auto-generated method stub //int a = 10 ;int b = 20; //System.out.println(a==b); Scanner sc = new Scanner(System.in); System.out.println("客官,您是堂吃还是外卖?1.堂吃; 2.外卖"); String s = sc.next(); String s2 = (s.equals("1")) ? "堂吃一位" : "外送一位"; System.out.println(s2); } }
if条件语句
第一种形式:
public class Hello123 { public static void main(String[] args) { // TODO Auto-generated method stub // TODO Auto-generated method stub float mian = 10.0f;//面的价格 float suan = 2.0f;//酸梅汤 float total_pay =0f;//总钱数 Scanner sc = new Scanner(System.in); //问用户要几碗面? System.out.println("请问您要几碗面?"); int num = sc.nextInt(); total_pay = num * mian; //问顾客需不需要饮料(饮料2元一杯) System.out.println("请问您是否需要饮料?Y/n"); String s = sc.next( ); if( s.equals("y")){ total_pay = total_pay + num * suan; } System.out.printf("您一共消费了%f元",total_pay); sc.close(); } }
第2种形式:
package demo1; import java.util.Scanner; public class Tangchi { public static void main(String[] args) { // TODO Auto-generated method stub Scanner sc = new Scanner(System.in); System.out.println("客官,请问您是堂吃还是外送?" +"1.堂吃/2.外送"); String s = sc.next(); if(s.equals("1")){ System.out.println("堂吃一位!"); }else{ System.out.println("外送一位!"); } } }
第3种形式:
package demo1; import java.util.Scanner; public class MianType { public static void main(String[] args) { // TODO Auto-generated method stub Scanner sc = new Scanner(System.in); System.out.println("客官,您几位?"); int num = sc.nextInt(); System.out.println("请问你们吃什么面?"); System.out.println("a.老北京炸酱面;b.刀削面" +"c.油泼面"); String s = sc.next(); if(s.equals("a")){ System.out.printf("老北京炸酱面%d碗",num); }else if(s.equals("b")){ System.out.printf("刀削面%d碗",num); }else if(s.equals("c")){ System.out.printf("油泼面%d碗",num); }else{ System.out.println("不好意思,您需求的面我们这里没有"); } } }
if语句的嵌套
询问顾客吃什么面,并询问其是否加蛋、加油渣 ?将结果反馈给后台。
if语句的多条件
import java.util.Scanner; public class happy09 { public static void main(String[] args) { // TODO Auto-generated method stub float price ;boolean fenqi;boolean firstpay; System.out.println("老板,请问手机多少钱?"); Scanner sc = new Scanner(System.in); price = sc.nextFloat(); System.out.println("老板,请问支不支持分期?"); fenqi = sc.nextBoolean(); System.out.println("老板,请问支不支持零首付?"); firstpay = sc.nextBoolean(); if(price <=1000 && fenqi == true && firstpay == true) { System.out.println("小Case!"); }else { System.out.println("太贵了,买不起~"); } } }
switch语句
package test; import java.util.Scanner; public class a7 { public static void main(String[] args) { // TODO 自动生成的方法存根 Scanner sc = new Scanner (System.in); while (true){ System.out.println("客观,请问您需要什么面:"); System.out.print("1.刀削面\n2.蛋黄面\n3.玉米面\n4.牛筋面\n5.幸福小丸仔面\n"); int m = sc.nextInt(); switch (m){ case 1: System.out.println("您选择的是刀削面"); break; case 2: System.out.println("您选择的是蛋黄面"); break; case 3: System.out.println("您选择的是玉米面"); break; case 4: System.out.println("您选择的是牛筋面"); break; case 5: System.out.println("您选择的是幸福小丸仔面"); break; default: System.out.println("对不起 输入错误"); break; } } } }
2.3重复迭代:循环结构
while循环
package test; import java.util.Scanner; public class a7 { public static void main(String[] args) { // TODO 自动生成的方法存根 Scanner sc = new Scanner (System.in); while (true){ System.out.println("客观,请问您需要什么面:"); System.out.print("1.刀削面\n2.蛋黄面\n3.玉米面\n4.牛筋面\n5.幸福小丸仔面\n"); int m = sc.nextInt(); switch (m){ case 1: System.out.println("您选择的是刀削面"); break; case 2: System.out.println("您选择的是蛋黄面"); break; case 3: System.out.println("您选择的是玉米面"); break; case 4: System.out.println("您选择的是牛筋面"); break; case 5: System.out.println("您选择的是幸福小丸仔面"); break; default: System.out.println("对不起 输入错误"); break; } } } }
for循环
public class test02 { public static void main(String[] args) { // TODO Auto-generated method stub //String a ="hello"; String [] menu = {"阳春面","油泼面","鸡汤面","火鸡面","安徽板面"}; for(int i=0;i <5;i++){ System.out.println(menu[i]); } } }
循环的嵌套
public class test03 { public static void main(String[] args) { // TODO Auto-generated method stub String [] menu = {"阳春面","油泼面","鸡汤面","火鸡面","安徽板面"}; String [] drink = {"可乐","啤酒","雪碧"}; for(int i=0;i<5;i++){ for(int j=0;j<3;j++){ System.out.println(menu[i]+"+"+drink[j]); } } } }
2.4 数据的存储--数组
Java一维数组
- 面馆老板现在需要重新定义一份菜单,使用一维数组,他有几种方法呢 ?
public class HelloWorld { public static void main(String []args) { //System.out.println("Hello World!"); String menu = new String[5]; menu[0] = "炸酱面"; menu[1] = "刀削面"; menu[2] = "安徽板面"; menu[3] = "葱油拌面"; menu[4] = "兰州拉面"; } }
Java二维数组
- 面馆老板现在需要根据周一到周五,每天推出三款特价面,利用二维数组,他该怎么做呢 ?
public class erweishuzu { public static void main(String[] args) { // TODO Auto-generated method stub //double [][] priec = new double [4] [3]; String [][] price = {{"炸酱面","方便面","版面"},{"刀削面","拉面","炒面"},{"牛肉面","鸡汤面","红烧面"},{"炒面","拉面","刀削面"},{"牛肉面","红烧面","鸡汤面"}}; for(int i=0;i<5;i++) { System.out.println("周"+(i+1)); for(int j = 0;j<3;j++) { System.out.println(price[i][j]); } } } }
Javva for语句循环遍历数组
- 面馆老板用foreach语句遍历打印每一种面。
任务三 JAVA面向对象程序编程(一)
3.1类和对象
类和对象
- 面馆按产品分类,可以分为几类?
面类,饮料类,小吃类
- 每一类有什么具体的产品(对象)?
面类的对象: 火鸡面,炸酱面,刀削面,油泼面 饮料类对象: 可乐,雪碧,芬达,啤酒,江小白 小吃类对象: 炸串,卤蛋,麻辣烫,辣白菜
类的成员变量和成员方法
需求分析(以面馆的面类产品为例):
面类: 名称; 类别:(干面,汤面,炒面) 价格; 份量; 口味; 数量 预定订单; 取消订单; 查看订单; 修改订单; 投诉店家;
- 面馆老板建立mian类,为它设计成员变量和成员方法
package 小马哥面馆; public class Noodle { //成员变量 //名称 public String name; //价格 public double price; //数量 public int num; /*构造方法*/ public Noodle(){ } public Noodle(String name,double price,int num){ this.name = name; this.price = price; this.num = num; } //成员方法 //预定订单; public void buy(String name,int num){ this.name =name; this.num = num; } //取消订单; public void cancel(String name,int n){ this.name =name; this.num = this.num -n; } //查看订单; public String lookup( ){ String s ="您订购的面是:\r\n"; s = "品名:"+ this.name +" 价格:"+ this.price +" 数量: "+ this.num; return s; } public static void main(String[] args) { // TODO Auto-generated method stub Noodle n1= new Noodle(); n1.name="手擀面"; n1.price = 10; n1.num = 2; System.out.println("您订的面是"+n1.name); System.out.println("价格:"+n1.price); System.out.println("数量"+ n1.num); Noodle n2 = new Noodle("炸酱面",12,3); System.out.println("您订的面是"+n2.name); System.out.println("价格:"+n2.price); System.out.println("数量"+ n2.num); Noodle n3 = new Noodle(); n3.buy("油泼面",2); n3.cancel("油泼面",1); String s2 =n3.lookup(); System.out.println(s2); } }
练习:怎样设计小吃类和饮料类 ?
3.2 成员变量的完善
为面类成员变量进行封装:
package happy0319; public class Noodle { //成员变量 //名称 private String name; //价格 private double price; //数量 private int num; /*构造方法*/ public Noodle(){ } public Noodle(String name,double price,int num){ this.name = name; this.price = price; this.num = num; } //成员方法 public String getName(){ return this.name; } public double getPrice(){ return this.price; } public int getNum(){ return this.num; } //写方法 public boolean setName(String s){ this.name = s; return true; } public boolean setPrice(double p){ this.price = p; return true; } public boolean setNum(int n){ this.num = n; return true; } public String toString(){ return "名称:" +this.name+"价格:"+ this.price + "数量: " + this.num; } public static void main(String[] args) { // TODO Auto-generated method stub Noodle n2 = new Noodle("炸酱面",12,3); System.out.println("您订的面是"+n2.getName()); System.out.println("价格:"+n2.getPrice()); System.out.println("数量"+ n2.getNum()); n2.setName("老北京炸酱面"); n2.setPrice(15); n2.setNum(2); System.out.println("订单变更:"); System.out.println("您订的面是"+n2.getName()); System.out.println("价格:"+n2.getPrice()); System.out.println("数量"+ n2.getNum()); } }
任务四 对象数组
package test2; public class Test { public static void main(String[] args) { // TODO Auto-generated method stub Noodle [] nl = new Noodle[3]; nl[0] = new Noodle("炸酱面",12.0,3); nl[1] = new Noodle("臊子面",14.0,2); nl[2] = new Noodle("刀削面",10.0,5); for(int i=0;i<3;i++){ if(nl[i].getName().equals("臊子面")){ System.out.println(nl[i].toString()); } } } }