编写一个java应用程序_编写一个简单java应用程序

import javax.swing.JOptionPane;

public class Du02 {

public static void main(String[] args) {

String aStr = JOptionPane.showInputDialog(null, "Please input side a for Trangle");

String bStr = JOptionPane.showInputDialog(null, "Please input side b for Trangle");

String cStr = JOptionPane.showInputDialog(null, "Please input side c for Trangle");

Trangle trangle = new Trangle();

trangle.setA(Double.parseDouble(aStr));

trangle.setB(Double.parseDouble(bStr));

trangle.setC(Double.parseDouble(cStr));

System.out.println("Area is: " + trangle.getArea());

System.out.println("perimeter is: " + trangle.getPerimeter());

Lader lader = new Lader(3, 7, 5);

System.out.println("Lader's area is: " + lader.getArea());

Circle c = new Circle(2);

System.out.println("Circle's area is: " + c.getArea());

System.out.println("Circle's perimeter is: " + c.getArea());

}

}

--------要修改的几个地方

class Trangle{

private double a, b, c;

private double area;

private double perimeter;

public double getArea() {

double p = (a+b + c) /2;

return Math.sqrt(p * (p-a)*(p-b)*((p-c)));

}

----------------------------

class Lader{//梯形周长不会算

private double a;

private double b;

private double h;

private double area;

public Lader(double a, double b, double h){

this.a = a;

this.b = b;

this.h = h;

}

----------------------------------------

class Circle{

private double r;

private double perimeter;

private double area;

public static final double PI = Math.PI;//圆周率你可以自己定义，譬如3.14,或者就用

//java自己带的PI

public Circle(double r){

this.r= r;

}

public double getArea() {

return PI * r * r;

}

public double getPerimeter() {

return 2 * PI * r;

}

}