主要内容

1. 学生类
2. 交通工具类
3. 圆类

一.学生类

具有属性：姓名、年龄、学位。由学生类派生出本科生类和研究生类，本科生类
增加属性：专业，研究生类增加属性：研究方向，每个类都有 show（）方法，用于输出属性信息。

1.源代码

代码如下（示例）:

package test;
class Student1{private String name;private int age;private String degree;public Student1(String name, int age, String degree) {super();//Java 的规定：子类继承父类，子类的构造方法必须调用//super（）即父类的构造方法，而且必须放在构造方法的第一行this.name = name;this.age = age;this.degree = degree;}public Student1() {super();}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 getDegree() {return degree;}public void setDegree(String degree) {this.degree = degree;}public void show(){System.out.println("姓名：" + this.getName() + " 年龄：" + this.getAge() 
+ " 学位：" + this.getDegree() );}
}
class Undergraduate extends Student1{ //本科类private String specialty;//专业public String getSpecialty() {return specialty;}public void setSpecialty(String specialty) {this.specialty = specialty;}public Undergraduate(String name, int age, String degree, String specialty) 
{super(name, age, degree);this.specialty = specialty;}public void show(){System.out.println("姓名：" + this.getName() + " 年龄：" + this.getAge() 
+ " 学位：" + this.getDegree() + " 专业：" + this.getSpecialty());}
}
class Graduate extends Student1{ //研究生类private String direction;public String getDirection() {return direction;}public void setDirection(String direction) {this.direction = direction;}public Graduate(String name, int age, String degree, String direction) {super(name, age, degree);this.direction = direction;}public void show(){System.out.println("姓名：" + this.getName() + " 年龄：" + this.getAge() 
+ " 学位：" + this.getDegree() + " 研究方向：" + this.getDirection());}
}
public class student {public static void main(String[] args) {Undergraduate stu1=new Undergraduate("张三",20,"本科","物联网工程");Graduate stu2=new Graduate("李四",24,"硕士","计算机科学与技术");stu1.show();stu2.show();}
}

2.结果

二.交通工具类

属性包括：速度、类别、颜色；方法包括：设置速度、设置颜色、取得类别、取得颜色。
设计一个小车类继承自交通工具类，新增属性：座位数，增加设置和获取座位数的方法，创建小车类对象，为其设置新的颜色和速度，并显示所有属性 信息。

1.源代码

代码如下（示例）:

class transport {private int speed;private String classify;private String color;transport(int speed,String classify,String color){this.speed=speed;this.classify=classify;this.color=color;}public int getspeed() {return speed;}public void setspeed(){this.speed=speed;}public String getclassify() {return classify;}public void setclassify(){this.classify=classify;}public String getcolor() {return color;}public void setcolor(){this.color=color;}public void show(){System.out.println("速度 "+this.getspeed()+" 类别
"+this.getclassify()+" 颜色 "+this.getcolor());}public static void main(String[] args) {car c1 = new car(100, "宝马", "白色", 4);c1.show();}
}
class car extends transport{private int number;public int getnumber() {return number;}public void setnumber(){this.number=number;}car(int speed,String classify,String color,int number){super(speed,classify,color);this.number=number;}public void show(){System.out.println("速度 "+this.getspeed()+" 类别
"+this.getclassify()+" 颜色 "+this.getcolor()+" 座位数
"+this.getnumber());}
}

2.结果

三.圆类

具有属性：圆心坐标 x和 y以及圆半径 r，具有设置和获取属性的方法，及计算周长和面积的方法。再设计一个圆柱体类继承自圆类，增加属性：高度，增加了设置和获取高度的方法，及计算表面积和计算体积的方法。创建圆柱体类对象，显示其所有属性信息，计算并显示其面积和体积。

1.源代码

代码如下（示例）:

package test;
class Circle {double x;double y;double r;Circle(double x, double y, double r) {this.x = x;this.y = y;this.r = r;}public void setX(double x) {this.x = x;}public void setY(double y) {this.y = y;}public void setR(double r) {this.r = r;}public double getX() {return x;}public double getY() {return y;}public double getR() {return r;}public double area() {return r * r * Math.PI;}public double perimeter() {return 2 * r * Math.PI;}public void show() {System.out.print("x=" + x + ", y=" + y + ", Radius=" + r);}
}
class Cylinder extends Circle {double h;Cylinder(double x, double y, double r, double h) {super(x, y, r);this.h = h;}public void setH(double h) {this.h = h;}public double getH() {return h;}public double area() {return perimeter() * h + super.area() * 2;}public double volume() {return super.area() * h;}public static void main(String[] args) {Cylinder cylinder = new Cylinder(2, 3, 4, 5);cylinder.show();System.out.println(", Height=" + cylinder.getH());System.out.println("面积=" + cylinder.area());System.out.println("体积=" + cylinder.volume());}
}

2.结果

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总结

以上是今天要讲的内容，学习了类继承。