import java.util.*;
interface I1{

    float getArea();

}
class Triangle implements I1
{
    float a;
    float b;
    float c;
    String s = "Triangle";

    Triangle (float a,float b,float c){
        this.a = a;
        this.b = b;
        this.c = c;

   
   
   
    }
    float getArea(){
        float p = (a + b + c) / 2;
        return Math.sqrt(p * (p - a) * (p - b) * (p - c ));

   
    }
}
    class Rectangle implements I1
    {
        float width;
        float length;
        String s = "Rectangle";
        float getArea(){
            return width * length;
       
        }
    };
    class Square implements I1
    {
        float a;
        String s = "Square";
        float getArea(){
            return a * a;
        }
    };
    class Circle implements I1
    {
        float r;
        String s = "Circle";
        final float PI = 3.1415926f;
        float getArea(){
            return PI*r*r;
        }
    };
    public void printArea(T){
        System.out.println("The area of this" + T.s + ":" + T.getArea() );
       
       
   
    }
    public class GraphicsTest
    {
        public static void main(String[] args){
            List<int>strList = new ArrayList<int>();
            strList.add(t.getArea());
            strList.add(r.getArea());
            strList.add(s.getArea());
            strList.add(c.getArea());
            Triangle t = new Triangle (3.3f,6.6f,5.5f);
           
            Rectangle r = new Retangle(5.6f,3.8f);
            printArea(r);
            Square s = new Square(2.9f);
            printArea(s);
            Circle c = new Circle(4.8f);
            printArea(c);
           
       
        }
    };

输出的错误结果：
E:\09008129>javac GraphicsTest.java
GraphicsTest.java:57: 需要为 class、interface 或 enum
        public void printArea(T){
               ^
GraphicsTest.java:62: 需要为 class、interface 或 enum
        }
        ^
2 错误
//这是什么意思啊！我这道题要求用泛型输出各种图形的面积，可是我似乎不大理解泛型，估计是泛型的那个方法写错了，应该怎么修改呢？为什么？还希望各位大虾帮忙解答！！小弟在这里谢过了！！

汗，你写的太业余了，不是一句两句能说清楚的~~~

你想要第五十七行的 printArea(T)做什么？
方法是要定义在类里面的

另外，代码还是要注意一下缩进和空行……
想给你排一下程序的，看了下代码，才明白二楼所说的含义！！！
建议楼主再回去好好看书，前面的先学扎实了，那些类，方法，成员变量等的定义和使用先学好了，再看这面向对象的知识……
估计二楼在看的时候，不是在找错的地方，而是在找对的地方……

import java.util.*;
interface I1{

    float getArea();
}

class Triangle implements I1
{
    float a;
    float b;
    float c;
    String s = "Triangle";

    Triangle (float a,float b,float c){
        this.a = a;
        this.b = b;
        this.c = c;
    }
    float getArea(){
        float p = (a + b + c) / 2;
        return Math.sqrt(p * (p - a) * (p - b) * (p - c ));
    }
}

class Rectangle implements I1
{
    float width;
    float length;
    String s = "Rectangle";
    float getArea(){
        return width * length;
    }
};  //这个分号是做什么？

class Square implements I1
{
    float a;
    String s = "Square";
    float getArea(){
        return a * a;
    }
};

class Circle implements I1
{
    float r;
    String s = "Circle";
    final float PI = 3.1415926f;
    float getArea(){
        return PI*r*r;
    }
};

public void printArea(T){
    System.out.println("The area of this" + T.s + ":" + T.getArea() );
}
public class GraphicsTest
{
    public static void main(String[] args){
        List<int>strList = new ArrayList<int>();
        strList.add(t.getArea());
        strList.add(r.getArea());
        strList.add(s.getArea());
        strList.add(c.getArea());
        Triangle t = new Triangle (3.3f,6.6f,5.5f);
       
        Rectangle r = new Retangle(5.6f,3.8f);
        printArea(r);
        Square s = new Square(2.9f);
        printArea(s);
        Circle c = new Circle(4.8f);
        printArea(c);
    }
};

[ 本帖最后由 洛云 于 2011-4-4 01:10 编辑 ]