java程序设计实用教程 书中代码.pdf

例2-1 Example2_1.java public class Example2_1 { public static void main(String args[]) { Rect rectangle1,rectangle2; //声明2 个对象 rectangle1 = new Rect(); //创建对象 rectangle2 = new Rect(); rectangle1.width=128; rectangle1.height=69; rectangle2.width=18.9; rectangle2.height=59.8; double area=rectangle1.getArea(); System.out.println(rectangle1 的面积:+area); area=rectangle2.getArea(); System.out.println(rectangle2 的面积:+area); } } 例2-2 Circle.java public class Circle { double radius; //圆的半径 double getArea() { return 3.1415926*radius; } } Lader.java public class Lader { double above; //梯形的上底 double bottom; //梯形的下底 double height; //梯形的高 double getArea() { return (above+bottom)*height/2; } } MainClass.java public class MainClass { public static void main(String args[]) { Circle circle=new Circle(); circle.radius=100; double area=circle.getArea(); System.out.println(圆的面积:+area); Lader lader=new Lader(); lader.above=10; lader.bottom=56; lader.height=8.9; area=lader.getArea(); System.out.println(梯形的面积:+area); } } 例2-3 Rectangle.java public class Rectangle //Rectangle 类 { double width; double height;