java写个类，写写注释就更好了

模仿circle类 /1、成员变量，针对类的属性 private int r; //2、成员方法，针对类的行为 public int getR()//get访问器，getter { return r; } public void setR(int a)//set访问器，setter { r = a; } public double getArea() { return Math.PI * r * r; }}

public class CircleTest { public static void main(String[] args) { // TODO Auto-generated method stub Circle c = new Circle(); c.setR(3); System.out.println("半径为" + c.getR() + "的圆的面积是" + c.getArea()); }}

写出矩形类、三角形类。随机生成100个长度和宽度范围在[1, 100]的矩形，然后对这些矩形排序。Rectangle[] a = new Rectangle[100];示例结果：第1大的矩形为：98 * 96 = ……第2大的矩形为：97 * 96 = ……第100大的矩形为：3 * 4 = 12

1、矩形类：

package cn.personal.demo06;

public class Rectangle {

    // 定义成员变量，宽和高
    private int width;
    private int heigh;

    // 添加有参构造方法
    public Rectangle(int width, int heigh) {
        super();
        this.width = width;
        this.heigh = heigh;
    }

    // 添加get/set方法
    public int getWidth() {
        return width;
    }

    public void setWidth(int width) {
        this.width = width;
    }

    public int getHeigh() {
        return heigh;
    }

    public void setHeigh(int heigh) {
        this.heigh = heigh;
    }

    //获取面积的方法
    public int getArea(int wi,int he) {
        return wi*he;
    }
}

2、矩形测试类

package cn.personal.demo06;

import java.util.Arrays;

public class RectangleTest {

    public static void main(String[] args) {

        // 定义Rectangle数组，长度为100；
        Rectangle[] rects = new Rectangle[100];
        
        // 定义Rectangle中的width数组，长度为100；
        int[] widths = new int[100];
        
        // 定义Rectangle中的height数组，长度为100；
        int[] heights = new int[100];
        
        for (int i = 0; i < rects.length; i++) {
            int wr=getRandon();
            int hr=getRandon();
            rects[i]=new Rectangle(wr, hr);
            widths[i] = rects[i].getWidth();
            heights[i] = rects[i].getHeigh();
        }

        //将宽度和高度进行升序排序
        Arrays.sort(widths);
        Arrays.sort(heights);
        
        //循环输出打印
        for (int i = 1; i <= rects.length; i++) {
            System.out.println("第"+i+"大的矩形为："
                    +widths[rects.length-i]+"*"+heights[rects.length-i]+"="
                    +rects[rects.length-i].getArea(widths[rects.length-i],heights[rects.length-i]));
        }
    }

    public static int getRandon() {
        return (int) (Math.random() * 99 + 1);
    }
}

3、矩形测试效果

1、三角形类

package cn.personal.demo06;

public class Triangle {
    
    //定义成员变量，三条边
    private int line1;
    private int line2;
    private int line3;

    //添加有参构造
    public Triangle(int line1, int line2, int line3) {
        super();
        this.line1 = line1;
        this.line2 = line2;
        this.line3 = line3;
    }
    
    //添加get/set方法
    public int getLine1() {
        return line1;
    }

    public void setLine1(int line1) {
        this.line1 = line1;
    }

    public int getLine2() {
        return line2;
    }

    public void setLine2(int line2) {
        this.line2 = line2;
    }

    public int getLine3() {
        return line3;
    }

    public void setLine3(int line3) {
        this.line3 = line3;
    }

    //添加求面积方法
    public double getArea() {
        double p = (line1 + line2 + line3) / 2d;
        return Math.sqrt(p * (p - line1) * (p - line2) * (p - line3));
    }

}

2、三角形测试类

package cn.personal.demo06;

public class TriangleTest {

    public static void main(String[] args) {

        Triangle triangle = new Triangle(3, 4, 5);
        System.out.println("三边长为" + triangle.getLine1() + ","
                + triangle.getLine2() + "," + triangle.getLine3() + "的三角形面积:"
                + triangle.getArea());
        triangle = new Triangle(6, 7, 8);
        System.out.println("三边长为" + triangle.getLine1() + ","
                + triangle.getLine2() + "," + triangle.getLine3() + "的三角形面积:"
                + triangle.getArea());
    }

}

3、三角形测试效果

有用必采纳不。
http://t.csdn.cn/LhSMV

import java.util.Arrays;
import java.util.Comparator;
import java.util.Random;

public class Main {
    public static void main(String[] args) {
        Random random = new Random();
        Rectangle[] rectangles = new Rectangle[100];
        for (int i = 0; i < rectangles.length; i++) {
            Rectangle rectangle = new Rectangle(random.nextInt(100) + 1,random.nextInt(100) + 1);
            rectangles[i] = rectangle;
        }
        Arrays.sort(rectangles, new Comparator<Rectangle>() {
            @Override
            public int compare(Rectangle o1, Rectangle o2) {
                int area1 = o1.getArea();
                int area2 = o2.getArea();
                return area1 -area2;
            }
        });
        for (int i = 0; i < rectangles.length; i++) {
            Rectangle rectangle = rectangles[i];
            System.out.println("第" + (i + 1) + "大的矩形为：" + rectangle.getHeight() + "*" + rectangle.getWidth() + "=" + rectangle.getArea());
        }

    }
}
class Rectangle {
    private int width;

    private int height;

    public Rectangle(){}

    public Rectangle(int width, int height) {
        super();
        this.width = width;
        this.height = height;
    }

    public int getWidth() {
        return width;
    }
    public int getHeight() {
        return height;
    }

    //获取面积
    public int getArea() {
        return width*height;
    }
}

package com.example.demo.csdn.test01;

import java.util.Arrays;
import java.util.Comparator;
import java.util.Random;
import java.util.stream.IntStream;

public class Rectangle {
    private int width;
    private int height;

    public int getArea() {
        return width * height;
    }

    public int getWidth() {
        return width;
    }

    public void setWidth(int width) {
        this.width = width;
    }

    public int getHeight() {
        return height;
    }

    public void setHeight(int height) {
        this.height = height;
    }

    public static void main(String[] args) {
        Random random = new Random(70);
        Rectangle[] rectangles = new Rectangle[100];
        for (int i = 0; i < rectangles.length; i++) {
            Rectangle rectangle = new Rectangle();
            rectangle.setWidth(random.nextInt(100) + 1);
            rectangle.setHeight(random.nextInt(100) + 1);
            rectangles[i] = rectangle;
        }
        Arrays.sort(rectangles, new Comparator<Rectangle>() {
            @Override
            public int compare(Rectangle o1, Rectangle o2) {
                int area1 = o1.getArea();
                int area2 = o2.getArea();
                return area1 == area2 ? 0 : (area1 > area2 ? -1 : 1);
            }
        });
        for (int i = 0; i < rectangles.length; i++) {
            Rectangle rectangle = rectangles[i];
            System.out.println("第" + (i + 1) + "大的矩形为：" + rectangle.getHeight() + "*" + rectangle.getWidth() + "=" + rectangle.getArea());
        }
    }
}

package com.example.demo.csdn.test01;

public class Triangle {
    private int line1;
    private int line2;
    private int line3;


    public double getArea() {
        double p = (line1 + line2 + line3) / 2d;
        return Math.sqrt(p * (p - line1) * (p - line2) * (p - line3));
    }

    public int getLine1() {
        return line1;
    }

    public void setLine1(int line1) {
        this.line1 = line1;
    }

    public int getLine2() {
        return line2;
    }

    public void setLine2(int line2) {
        this.line2 = line2;
    }

    public int getLine3() {
        return line3;
    }

    public void setLine3(int line3) {
        this.line3 = line3;
    }

    public static void main(String[] args) {
        Triangle triangle = new Triangle();
        triangle.setLine1(3);
        triangle.setLine2(4);
        triangle.setLine3(5);
        System.out.println("三边长为" + triangle.getLine1() + "," + triangle.getLine2() + "," + triangle.getLine3() + "的三角形面积:" + triangle.getArea());
        triangle.setLine1(5);
        triangle.setLine2(12);
        triangle.setLine3(13);
        System.out.println("三边长为" + triangle.getLine1() + "," + triangle.getLine2() + "," + triangle.getLine3() + "的三角形面积:" + triangle.getArea());
    }
}

矩形类：

/**
 * 矩形
 */
public class Rectangle implements Comparable<Rectangle>{
    
    //类属性h，也就是矩形的高
    private int h;
    
    //类属性w，也就是矩形的宽
    private int w;
    

    //类行为方法，get访问器，获取属性h的值
    public int getH() {
        return h;
    }

    //类行为方法，set访问器，给属性h赋值
    public void setH(int h) {
        this.h = h;
    }
    
    //类行为方法，get访问器，获取属性w的值
    public int getW() {
        return w;
    }

    //类行为方法，set访问器，给属性w赋值
    public void setW(int w) {
        this.w = w;
    }
    
    //计算矩形面积
    public double getArea() {
        return h*w;
    }
    
    //重写排序方法，根据面积大小排序
    @Override
    public int compareTo(Rectangle r) {
        return (int) (r.getArea()-this.getArea());
        
    }

}

矩形测试：

import java.util.Arrays;

public class RectangleTest {
    
    public static void main(String args[]) {
        //容量为100的数组，存放生成的10的矩形
        Rectangle[] rectangleArr = new Rectangle[100];
        //循环100次，生成100个矩形
        for(int i=0; i<100; i++) {
            //创建Circle类对象
            Rectangle r = new Rectangle();
            //给矩形属性h赋值3，也就是设置该矩形的高为3,Math.random()获取随机数
            r.setH((int)(Math.random()*100+1));
            //给矩形属性w赋值4，也就是设置该矩形的宽为4,Math.random()获取随机数
            r.setW((int)(Math.random()*100+1));
            //放入数组
            rectangleArr[i] = r;
        }
        //对数组内的矩形面积进行排序
        Arrays.sort(rectangleArr);
        
        //排序后输出
        for(int i=0; i<100; i++) {
            System.out.println("第" +( i+1) + "大矩形为：" + rectangleArr[i].getW() + "*" + rectangleArr[i].getH() + "=" + rectangleArr[i].getArea());
        }
        
    }
}

结果：

三角形类：

/**
 * 三角形
 */
public class Triangle {
    
    //类属性a,三角西的一条边
    private int a;
    
    //类属性b,三角西的一条边
    private int b;
        
    //类属性c,三角西的一条边
    private int c;

    //类行为方法，get访问器，获取属性a的值
    public int getA() {
        return a;
    }

    //类行为方法，set访问器，给属性a赋值
    public void setA(int a) {
        this.a = a;
    }
    
    //类行为方法，get访问器，获取属性b的值
    public int getB() {
        return b;
    }

    //类行为方法，set访问器，给属性b赋值
    public void setB(int b) {
        this.b = b;
    }
    
    //类行为方法，get访问器，获取属性c的值
    public int getC() {
        return c;
    }

    //类行为方法，set访问器，给属性c赋值
    public void setC(int c) {
        this.c = c;
    }
    
    //计算三角形面积
    public double getArea() {
        //海伦公式求三角形面积
        double p = (a+b+c)/2;
        return Math.sqrt((p*(p-a)*(p-b)*(p-c)));
    }

}

package com.ly.csdn.test;

import lombok.Builder;
import lombok.Data;

import java.awt.*;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Random;

@Data
@Builder
public class TestRectangleDemo {

    //类属性长
    private int length;

    //类属性宽
    private int width;

    //类属性高
    private int height;
    
    /**
     * 计算矩形面积
     *
     * @return
     */
    public int getArea() {
        return width * height;
    }

    /**
     * 计算三角形面积
     */
    public double getDeltaArea() {
        //求三角形面积根据海伦公式
        double p = (length + width + height) / 2;
        return Math.sqrt((p * (p - length) * (p - width) * (p - height)));
    }

    public static void main(String[] args) {
        Random random = new Random(70);
        TestRectangleDemo[] r = new TestRectangleDemo[100];
        for (int i = 0; i < r.length; i++) {
            TestRectangleDemo testRectangleDemo =TestRectangleDemo.builder().width(random.nextInt(100) + 1)
                    .height(random.nextInt(100) + 1).build();;
            r[i] = testRectangleDemo;
        }
        Arrays.sort(r, new Comparator<TestRectangleDemo>() {
            @Override
            public int compare(TestRectangleDemo o1, TestRectangleDemo o2) {
                int area1 = o1.getArea();
                int area2 = o2.getArea();
                return area1 == area2 ? 0 : (area1 > area2 ? -1 : 1);
            }
        });
        //计算矩形输出结果
        for (int i = 0; i < r.length; i++) {
            TestRectangleDemo rectangle = r[i];
            System.out.println("第" + (i + 1) + "大的矩形为：" + rectangle.getHeight() + "*" + rectangle.getWidth() + "=" + rectangle.getArea());
        }
        //计算三角形输出结果
        TestRectangleDemo testRectangleDemo = TestRectangleDemo.builder().length(1).width(2).height(3).build();
        System.out.println("三边长为：" + testRectangleDemo.getLength() + "宽为：" + testRectangleDemo.getWidth()
                + "高为：" + testRectangleDemo.getHeight() + "的三角形面积:" + testRectangleDemo.getDeltaArea());
    }

}

海伦公式

运行结果截图，望采纳===