playcircle.java

实现了《算法设计与分析》的一次课后题

import java.util.*;


public class PlayCircle {
	
	public static final double PI=3.14159;
	private double diameter;

	/**
	 * @param args
	 */
	public PlayCircle(){};
	public static void main(String[] args) {
		PlayCircle circle=new PlayCircle();
		circle.setDiameter(2);
		System.out.println("If circle has diameter 2");
		circle.showArea();
		System.out.println("Now you choose the diameter:");
		areaDialog();

	}

	private static void areaDialog() {
		Scanner keyboard=new Scanner(System.in);
		System.out.println("Enter the diameter of a circle:");
		double newDiameter=keyboard.nextDouble();
		PlayCircle c=new PlayCircle();
		c.setDiameter(newDiameter);
		c.showArea();
		
	}

	private void showArea() {
		System.out.println("Area is"+area(diameter/2));
		
	}

	public static Object area(double radius) {
		
		return (PI*radius*radius);
	}
	private void setDiameter(double newDiameter) {
		
		diameter=newDiameter;
		
	}

}