Java---面向对象
一.面向对象
1.概念
1.1面向过程 C
吃饭：动作为核心
起身--》开门--》大量的逻辑判断
1.2面向对象 C++/Java/Python/Go
目标：吃饭
人（忽略）吃饭
站在人类的角度思考问题
2.什么是对象？
Object-->东西(万事万物皆是对象。)
2.1类
类：抽象，一个设计，对象的抽象
对象：具体，类的具体
类 -----> 对象
狗 ---> Dog ---> 抽象的
（两只耳朵，一只尾巴，四条腿，一张嘴，毛发）----特征
（陪伴（动作，行为））----职责
Class ---> Type
public class Dog {//狗的信息int leg = 4;String hair = "金黄色";double price = 666.66;public void run(){System.out.println("我的狗跑的飞快!");}public void accompany(){System.out.println("带来快乐...");}public static void main(String[] args) {Dog myDog = new Dog();myDog.run();myDog.accompany();}
}3.以冰箱(Fridge)为例
1.名字(Fridge)
2.属性、特征、域(field)、xxx变量
3.方法、函数、动作
3.1Java的注释
*类、方法
/****/*行注释
//*块注释
/***/3.2冰箱的类
属性、方法
3.3执行冰箱操作
升高温度、降低温度工作
3.4异常情况
限制温度
import javax.swing.*;//冰箱类
public class Fridge {private String brand;private String color;private double size;private double weight;private double price;private int year;//保修年限private int temperature = 5;//温度private String company;//公司public String getBrand() {return brand;}//给汽车的brand设置品牌public void setBrand(String brand) {this.brand = brand;}public String getColor() {return color;}public void setColor(String color) {this.color = color;}public double getSize() {return size;}public void setSize(double size) {this.size = size;}public double getWeight() {return weight;}public void setWeight(double weight) {this.weight = weight;}public double getPrice() {return price;}public void setPrice(double price) {this.price = price;}public int getYear() {return year;}public void setYear(int year) {this.year = year;}public int getTemperature() {return temperature;}public void setTemperature(int temperature) {this.temperature = temperature;}public String getCompany() {return company;}public void setCompany(String company) {this.company = company;}//冰箱升高的温度方法// n 要升高的温度public void tempUp(int n){if (temperature+n > 20){JOptionPane.showMessageDialog(null,"温度超出冰箱范围，升温失败");}else {temperature += n;}}//冰箱降低的温度方法// n 要降低的温度public void tempDown(int n){if (temperature-n < -20){JOptionPane.showMessageDialog(null,"温度超出冰箱范围，降温失败");}else {temperature -= n;}}//显示当前冰箱的温度public void print(){System.out.println("当前温度:" + temperature);}public static void main(String[] args) {Fridge myFridge = new Fridge();myFridge.setBrand("无敌");System.out.println(myFridge.getBrand());System.out.println("冰箱启动");myFridge.print();while (true){String opt = JOptionPane.showInputDialog("请选择操作(1-升温,2-降温)");//String s = null;int n = 0;if ("1".equals(opt)) {//升温操作//String s = JOptionPane.showInputDialog("请输入要升高的度数");n = Integer.parseInt(JOptionPane.showInputDialog("请输入要升高的度数"));myFridge.tempUp(n);}else if ("2".equals(opt)){//降温操作//s = JOptionPane.showInputDialog("请输入要降低的度数");n = Integer.parseInt(JOptionPane.showInputDialog("请输入要降低的度数"));myFridge.tempDown(n);}myFridge.print();//判断是否退出操作int c = JOptionPane.showConfirmDialog(null,"是否继续进行");if (0 != c){JOptionPane.showMessageDialog(null,"操作完成，谢谢使用");break;}}}
}4.面向对象描述类
4.1文字描述
4.2代码描述
4.3类图描述
5.访问控制符
5.1 public---公开类型
任何代码都能访问
5.2 private---私有的
private String brand;private String color;private double size;private double weight;private double price;private int year;//保修年限private int temperature = 5;//温度private String company;//公司只有在本class内可以访问
6.属性操作
public String getBrand() {return brand;}//给汽车的brand设置品牌public void setBrand(String brand) {this.brand = brand;}public String getColor() {return color;}public void setColor(String color) {this.color = color;}public double getSize() {return size;}public void setSize(double size) {this.size = size;}public double getWeight() {return weight;}public void setWeight(double weight) {this.weight = weight;}public double getPrice() {return price;}public void setPrice(double price) {this.price = price;}public int getYear() {return year;}public void setYear(int year) {this.year = year;}public int getTemperature() {return temperature;}public void setTemperature(int temperature) {this.temperature = temperature;}public String getCompany() {return company;}public void setCompany(String company) {this.company = company;}setter / getter方式
通过setXXX(参数)存储
通过getXXX()取出数据
7.this关键字
//给汽车的brand设置品牌public void setBrand(String brand) {this.brand = brand;}this ----- 当前对象
this.brand = brand; //当前对象的属性brand，值为传入的变量brand的值