java创建抽象类

⑴ 编写一个完整的 java 程序，要求: (1)定义一个抽象类 Shape，在该类中:添加抽象方法

public abstract class Shape {
public abstract double Area();
public abstract void printArea();
}

class Circle extends Shape {
int radius;

public Circle(int radius) {
this.radius = radius;
}

@Override
public double Area() {
return Math.pow(this.radius, 2) * Math.PI;
}

@Override
public void printArea() {
// String.format("%.2f", Area()) 保留两位小数
System.out.println("半径为 " + this.radius + " 的圆的面积是 " + String.format("%.2f", Area()));
}
}

class Test {
public static void main(String[] args) {
// 生成一个 1 - 9 的随机整数
int radius = (int) (Math.random() * 9) + 1;
// 创建一个 Circle 对象实例
Circle circle = new Circle(radius);
// 调用 printArea() 方法打印面积
circle.printArea();
}
}

⑵ 浣跨敤java 瀹氫箟鎶借薄绫伙細public abstract class Person

浠ｇ爜濡備笅銆備负浜嗘樉绀烘柟渚挎墍浠ュ啓鍦ㄥ悓涓涓鏂囦欢閲岄潰浜嗐

publicclassTest{
	publicstaticvoidmain(String...args)throwsException{
		Personstu1=newStudent();
		stu1.preWork();
		stu1.work();
		stu1.reWork();
		stu1.doHomework();
		Persontea1=newTeacher();
		tea1.preWork();
		tea1.work();
		tea1.reWork();
		tea1.doHomework();
	}

}

abstractclassPerson{
	publicabstractvoidpreWork();

	publicabstractvoidwork();

	publicabstractvoidreWork();

	publicabstractvoiddoHomework();
}

classStudentextendsPerson{
	publicvoidpreWork(){
		System.out.println("棰勪範");
	}

	publicvoidwork(){
		System.out.println("涓婅");
	}

	publicvoidreWork(){
		System.out.println("澶嶄範");
	}

	publicvoiddoHomework(){
		System.out.println("鍐欎綔涓");
	}
}

classTeacherextendsPerson{
	publicvoidpreWork(){
		System.out.println("澶囪");
	}

	publicvoidwork(){
		System.out.println("涓婅");
	}

	publicvoidreWork(){
		System.out.println("杈呭");
	}

	publicvoiddoHomework(){
		System.out.println("鎵逛綔涓");
	}
}

⑶ java绋嬪簭棰橈細瀹氫箟涓涓鎶借薄绫-姘存灉,鍏朵腑鍖呮嫭getWeight()鏂规硶,缂栧啓绋嬪簭鍒嗗埆鍒涘缓鑻规灉銆

姘存灉绫

abstractpublicclassFruit{
	abstractpublicdoublegetWeight();
}

鑻规灉绫

publicclassAppleextendsFruit{
	privatedoubleweight;

	publicApple(doubleweight){
		this.weight=weight;
	}

	@Override
	publicdoublegetWeight(){
		returnweight;
	}

}

姗樺瓙绫

publicclassOrangeextendsFruit{
	privatedoubleweight;

	publicOrange(doubleweight){
		this.weight=weight;
	}

	@Override
	publicdoublegetWeight(){
		returnweight;
	}

}

妗冨瓙绫

publicclassPeachextendsFruit{
	privatedoubleweight;
	
	publicPeach(doubleweight){
		this.weight=weight;
	}

	@Override
	publicdoublegetWeight(){
		returnweight;
	}
}

涓荤被

publicclassMain{
	publicstaticvoidmain(String[]args){
		//TODOAuto-generatedmethodstub
		Fruit[]fruits={newPeach(12),newApple(2),newOrange(5)};
		for(Fruitfruit:fruits){
			System.out.println(fruit.getClass().getName()+"鐨勯噸閲忔槸"
					+fruit.getWeight());
		}
	}
}

杩愯岀粨鏋

Peach鐨勯噸閲忔槸 12.0

Apple鐨勯噸閲忔槸 2.0

Orange鐨勯噸閲忔槸 5.0

⑷ JAVA程序编写。 定义一个抽象类shape ，用来表示一般图形。

Java程序：

publicclassMain{	
	publicstaticvoidmain(String[]args){
		Shapes=null;
		s=newCircle(3);
		
		System.out.println("圆的面积："+s.area());
		System.out.println("圆的周长："+s.perimeter());
	}
}

/**
*形状类：抽象类
*@authordeveloper
*@version2017.05.23
*/
abstractclassShape{
	/**
	*计算形状的面积
	*@return形状的面积
	*/
	abstractdoublearea();
	
	/**
	*计算形状的周长
	*@return形状的周长
	*/
	abstractdoubleperimeter();
}

/**
*圆类
*@authordeveloper
*@version2017.05.23
*/
classCircleextendsShape{
	/**
	*半径
	*/
	protecteddoubleradius;
	
	/**
	*构造方法
	*@paramradius半径
	*/
	publicCircle(doubleradius){
		this.radius=radius;
	}

	@Override
	doublearea(){
		returnMath.PI*radius*radius;
	}

	@Override
	doubleperimeter(){
		return2*Math.PI*radius;
	}
}

运行测试：

圆的面积：28.274333882308138
圆的周长：18.84955592153876