class Rectangle {
    int Length;
    int Width;
    int Area;
    int circumference;
    public void Rrectangle(int length, int width) {
        this.Length = length;
        this.Width = width;
    }
    public int getLength() {
        return Length;
    }
    public  int setLength(int length) {
        return this.Length = length;
    }
    public int getWidth() {
        return Width;
    }
    public void setWidth(int width) {
        this.Width = width;
    }
    public int getArea(int length,int width){
        return length*width;
    }
    public int getCircumference(int length,int width){
        return 2*(length+width);
    }
}

import *;
import java.util.*;
public class Main{
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int maxArea = 0;
        int maxCircumference=0;
        int indexA = 0;
        int indexC;
        int area;
        int circumference;
        Scanner cin=new Scanner(System.in);
        Rectangle[]  a=new Rectangle[10];
        Rectangle[]  b=new Rectangle[10];
        System.out.print("请输入有几组数据");
        int n=cin.nextInt();
        for(int i=1;i<=n;i++)
        {
            int length=cin.nextInt();
            int width=cin.nextInt();
            a[i].Length=length;
            a[i].Width=width;
            a[i].Area=length*width;
            a[i].circumference=2*(length+width);
            if(a[i].Area>maxArea)
            {
                indexA=i;
            }
            if(a[i].circumference>maxCircumference)
            {
                indexC=i;
            }
        }
        System.out.print("面积最大的矩形的长为："+a[indexA].Length+"宽为："+a[indexA].Width+"最大面积为:"+maxArea);
    }
}

找出最大面积和周长的矩形！但是有异常！不知道哪里不对

呵呵

    问题很多：
1.
int Length;
    int Width;
    int Area;
    int circumference;
类参数应该设置为private类型，
   2.
         a[i].Length=length;
            a[i].Width=width;
            a[i].Area=length*width;
            a[i].circumference=2*(length+width);
这种访问不安全
 3.   public void Rrectangle(int length, int width) {
        this.Length = length;
        this.Width = width;
    }

非构造函数
4.
        Rectangle[]  b=new Rectangle[10];
        System.out.print("请输入有几组数据");
        int n=cin.nextInt();
        for(int i=1;i<=n;i++)
n大于等于10的时候数组越界；且数组应从0开始