用Java分解圆形（求半径、周长、面积）。

public class Yuan {
   
   
	private double ban;
	public Yuan(double ban){
   
   
			this.ban = ban;
	}
	public Yuan(){
   
   
	}	
	public void setBan(double ban) {
   
   
		this.ban = ban;
	}
	public double getban(){
   
   
		return ban;
	<