分了四個類class，用于保證內部繼承屬性的Sharp，矩形（Rectangle），圓（Circle）和調試用（initial）；

Sharp:

package?com.test2;

public?abstract?class?Sharp?{
	public?abstract?void?length();
	public?abstract?void?aera();
}

沒什么說的就是個模板；

Circle：

package?com.test2;

public?class?Circle?extends?Sharp?{
	public?final?double?pi?=?3.1415926;
	public?double?r;
	public?void?getR(double?r){
		this.r=r;
	}
	@Override
	public?void?length()?{
		//?TODO?Auto-generated?method?stub
		double?length?=?2*pi*r;
		System.out.println("the?Circle's?length?is?"+length);
	}

	@Override
	public?void?aera()?{
		//?TODO?Auto-generated?method?stub
		double?aera?=?pi*r*r;
		System.out.println("the?Circle's?aera?is?"+aera);
	}

}

繼承Sharp，用getR將R分開；?

Rectangle：

package?com.test2;

public?class?Rectangle?extends?Sharp?{
	public?int?Long;
	public?int?wide;
	public?void?getLong(int?Long?,int?wide){
		this.Long?=?Long;
		this.wide=?wide;		
	}
	@Override
	public?void?length()?{
		//?TODO?Auto-generated?method?stub
		int?length?=?2*(Long+wide);
		System.out.println("the?Rentangle's?length?is?"+length);
	}

	@Override
	public?void?aera()?{
		//?TODO?Auto-generated?method?stub
		int?aera?=?Long*wide;
		System.out.println("the?Rentangle's?area?is?"+aera);
	}

}

用?getLong（int，int）獲得長，寬；

initail：

package?com.test2;
import?java.util.Scanner;

public?class?Initail?{
	public?static?void?main(String[]?args)?{
		//?TODO?Auto-generated?method?stub
		System.out.println("enter?1?for?Rectangle?,0?for?Circle");
		Scanner?scan?=?new?Scanner(System.in);
		int?i?=(int)scan.nextDouble();
		switch(i){
		case?0:
			System.out.println("please?enter?r?of?the?Circle:");
			Circle?cir?=?new?Circle();
			cir.getR(scan.nextDouble());
			cir.length();
			cir.aera();
			break;
		case?1:
			Rectangle?rectan?=?new?Rectangle();
			System.out.println("please?enter?the?long?and?wide?of?the?Rectangle:");
			rectan.getLong((int)scan.nextDouble(),(int)scan.nextDouble());
			rectan.length();
			rectan.aera();
		}
		}
	}

常規輸出，還可以把輸出再放到一個方法里面，避免寫兩條

rectan.length();

rectan.aera();

我懶就省了...

運行結果：