代码

/*第一题：（1）定义接口A，里面包含值为3.14的常量PI和抽象方法double area()。（2）定义接口B，里面包含抽象方法void setColor(String c)。（3）定义接口C，该接口继承了接口A和B，里面包含抽象方法void volume()。（4）定义圆柱体类Cylinder实现接口C，该类中包含三个成员变量：底圆半径radius、圆柱体的高height、颜色color。（5）创建主类来测试类Cylinder。*/public class Homework1 {public static void main(String[] args) {C cylinder = new Cylinder(2,2,"黑色");System.out.println(cylinder);}}//定义接口A，里面包含值为3.14的常量PI和抽象方法double area()interface A{double PI = 3.14;double area();}//定义接口B，里面包含抽象方法void setColor(String c)interface B{void setColor(String c);}//定义接口C，该接口继承了接口A和B，里面包含抽象方法void volume()interface C extends A, B{double volume();}//定义圆柱体类Cylinder实现接口C，该类中包含三个成员变量：//底圆半径radius、圆柱体的高height、颜色colorclass Cylinder implements C{//底圆半径private double radius;private double height;private String color;//constructorpublic Cylinder() {}public Cylinder(double radius, double height, String color) {this.radius = radius;this.height = height;this.color = color;}//setter and getterpublic double getRadius() {return radius;}public void setRadius(double radius) {this.radius = radius;}public double getHeight() {return height;}public void setHeight(double height) {this.height = height;}public String getColor() {return color;}@Overridepublic double area() {return this.getRadius()*this.getRadius()*PI;}@Overridepublic void setColor(String c) {this.color = c;}@Overridepublic double volume() {return this.area()*this.getHeight();}@Overridepublic String toString() {return "Cylinder{" +"radius=" + radius +", height=" + height +", color='" + color + '\'' +'}';}}

（1）定义接口A 里面包含值为3.14的常量PI和抽象方法double area()。 （2）定义接口B 里面包含抽象方法void setColor(String c)。