使用抽象类写一个shape类出错了。错误信息：需要 ".class"，不是语句，需要 ";"等

[wx3046]

大家帮我看下这是什么错误，谢谢

代码：
//定义一个抽象Shape类
abstract class Shape {
int area;//面积
int perim;//周长
void getArea();
void getPerim();
}

//继承Shape类，定义Rectangle类
class Rectangles extends Shape
{
int length = 3,width = 4;

public void getArea(){
area = length * width;
System.out.println("Rectangle's area : " + area);
}

public void getPerim(){
perim = 2 * (length + width);
System.out.println("Rectangle's area : " + perim);
}
}

//继承Shape类，定义Cirle类
class Circle extends Shape
{
int r = 2;
float PI = 3.14;

public void getArea(){
area = int(PI * r *r);
System.out.println("Circle's area : " + area);
}

public void getPerim(){
perim = int(2 * PI * r);
System.out.println("Circle's perim : " + perim);
}
}

//继承Rectangle类，定义Square类

class ShapeClass
{
public static void main(String[] args){

System.out.println("Test Shape:");

Rectangles r = new Rectangles();
r.getArea();
r.getPerim();

Circle c = new Circle();
c.getArea();
c.getPerim();

// Square s = new Square();
// s.getArea();
// s.getPerim();
}
}





错误提示：
---------- javac ----------
ShapeClass.java:32: 需要 ".class"
area = int(PI * r *r);
^
ShapeClass.java:32: 不是语句
area = int(PI * r *r);
^
ShapeClass.java:32: 需要 ';'
area = int(PI * r *r);
^
ShapeClass.java:37: 需要 ".class"
perim = int(2 * PI * r);
^
ShapeClass.java:37: 不是语句
perim = int(2 * PI * r);
^
ShapeClass.java:37: 需要 ';'
perim = int(2 * PI * r);
^
6 错误

输出完成 (耗时: 0 秒)

[twinsken]

抽象类中的抽象方法也要声明 类型转换错误
改后的为
abstract class Shape {
int area;//面积
int perim;//周长
abstract void getArea();
abstract void getPerim();
}

//继承Shape类，定义Rectangle类
class Rectangles extends Shape
{
int length = 3,width = 4;

public void getArea(){
area = length * width;
System.out.println("Rectangle's area : " + area);
}

public void getPerim(){
perim = 2 * (length + width);
System.out.println("Rectangle's area : " + perim);
}
}

//继承Shape类，定义Cirle类
class Circle extends Shape
{
int r = 2;
float PI = (float) 3.14;

public void getArea(){
area = (int) (PI * r *r);
System.out.println("Circle's area : " + area);
}

public void getPerim(){
perim = (int) (2 * PI * r);
System.out.println("Circle's perim : " + perim);
}
}

//继承Rectangle类，定义Square类

class ShapeClass
{
public static void main(String[] args){

System.out.println("Test Shape:");

Rectangles r = new Rectangles();
r.getArea();
r.getPerim();

Circle c = new Circle();
c.getArea();
c.getPerim();

// Square s = new Square();
// s.getArea();
// s.getPerim();
}
}

[huangan0301]

abstract class Shape { 
int area;//面积 
int perim;//周长 
void getArea(); 
void getPerim(); 
}

你这是抽象类不是接口，抽象类中的方法不写abstract不会默认加abstract，你需要自己加上，你改为

public abstract void getArea();
public abstract void getPerim();
试试

[wx3046]

嗯，确实抽象方法那和类型转换那错了。谢谢两位

[ty_tarena_pger]

唉,我啥也不说了,基础实在是太那个了,好好努力吧

public abstract class Shape {
	int area;// 面积

	int perim;// 周长

	abstract void getArea();

	abstract void getPerim();
}

public class Circle extends Shape {
	int r = 2;

	static final double PI = 3.14;

	public void getArea() {
		double area = PI * r * r;
		System.out.println("Circle's area : " + area);
	}

	public void getPerim() {
		double perim = 2 * PI * r;
		;
		System.out.println("Circle's perim : " + perim);
	}
}

public class Rectangles extends Shape {
	int length = 3, width = 4;

	public void getArea() {
		area = length * width;
		System.out.println("Rectangle's area : " + area);
	}

	public void getPerim() {
		perim = 2 * (length + width);
		System.out.println("Rectangle's area : " + perim);
	}

}

public class ShapeClass {
	public static void main(String[] args) {

		System.out.println("Test Shape:");

		Rectangles r = new Rectangles();
		r.getArea();
		r.getPerim();

		Circle c = new Circle();
		c.getArea();
		c.getPerim();

		// Square s = new Square();
		// s.getArea();
		// s.getPerim();
	}
}

[ty_tarena_pger]

Test Shape:
Rectangle's area : 12
Rectangle's area : 14
Circle's area : 12.56
Circle's perim : 12.56