多态与接口题7似题3-接口及接口的实现

类对接口的实现：

package zuoye67;

public class Circle implements Figure{
	private int bian1;
	private int bian2;
	private int bian3;
	public void setbian1(int bian1){
		this.bian1 = bian1;
	}
	public int getbian1(){
		return bian1;
	}
	public void setbian2(int bian2){
		this.bian2 = bian2;
	}
	public int getbian2(){
		return bian2;
	}
	public void setbian3(int bian3){
		this.bian3 = bian3;
	}
	public int getbian3(){
		return bian3;
	}
	public Circle(){
		
	}
	public Circle (int bian1,int bian2,int bian3){
		this.bian1 = bian1;
		this.bian2 = bian2;
		this.bian3 = bian3;
	}
	
	public double area() {
		int a = bian1;
		int b = bian2;
		int c = bian3;
		if(a>0&&b>0&&c>0&&(a+b)>c&&(a+c)>b&&(b+c)>a){
		int p = (bian1+bian2+bian3)/2;
		return Math.sqrt(p*(p-bian1)*(p-bian2)*(p-bian3));
	}
		else return 0;
	}
	
	public double circumference() {
		int a = bian1;
		int b = bian2;
		int c = bian3;
		if(a>0&&b>0&&c>0&&(a+b)>c&&(a+c)>b&&(b+c)>a){
		return bian1+bian2+bian3;
	}else return 0;
	}
}

使用implements需要实现所有抽象方法。
使用abstract Arraylist可实现部分实现（刚才c++老师才讲java（狗头保命））
接口的定义：

package zuoye67;

public interface Figure {
	  double area();
	  double circumference();
}