用java定义Rectangle类（矩形类）,矩形的宽度和高度为double类型变量with，height；从键盘为with，height变量输入值，计算矩形的面积及周长。

以下是Java代码实现：

import java.util.Scanner;

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

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

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

    public double getPerimeter() {
        return 2 * (width + height);
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入矩形的宽度：");
        double width = scanner.nextDouble();
        System.out.print("请输入矩形的高度：");
        double height = scanner.nextDouble();
        Rectangle rectangle = new Rectangle(width, height);
        System.out.println("矩形的面积为：" + rectangle.getArea());
        System.out.println("矩形的周长为：" + rectangle.getPerimeter());
    }
}

运行结果示例：

请输入矩形的宽度：3.2
请输入矩形的高度：4.5
矩形的面积为：14.399999999999999
矩形的周长为：15.4