用Java编写接口实现，测试类中，有三个柱体，分别以三角形，圆形，矩形为底面积，求它们的体积。 测试用例：:三角形边：（3，4，5）;圆形半径：2; 矩形边（3，4），柱体高：6.

以下是Java代码实现，用于计算三个柱体的体积：

public interface Geometry {
    double getArea();
    double getCircum();
}

class Circle implements Geometry {
    private double radius;
    public Circle(double radius) {
        this.radius = radius;
    }
    public double getArea() {
        return Math.PI * radius * radius;
    }
    public double getCircum() {
        return 2 * Math.PI * radius;
    }
}

class Rectangle implements Geometry {
    private double length;
    private double width;
    public Rectangle(double length, double width) {
        this.length = length;
        this.width = width;
    }
    public double getArea() {
        return length * width;
    }
    public double getCircum() {
        return 2 * (length + width);
    }
}

class Square implements Geometry {
    private double side;
    public Square(double side) {
        this.side = side;
    }
    public double getArea() {
        return side * side;
    }
    public double getCircum() {
        return 4 * side;
    }
}

class Triangle implements Geometry {
    private double a;
    private double b;
    private double c;
    public Triangle(double a, double b, double c) {
        this.a = a;
        this.b = b;
        this.c = c;
    }
    public double getArea() {
        double p = (a + b + c) / 2;
        return Math.sqrt(p * (p - a) * (p - b) * (p - c));
    }
    public double getCircum() {
        return a + b + c;
    }
}

class Cylinder {
    private Geometry base;
    private double height;
    public Cylinder(Geometry base, double height) {
        this.base = base;
        this.height = height;
    }
    public double getVolume() {
        return base.getArea() * height;
    }
    public double getSurfaceArea() {
        return base.getCircum() * height + 2 * base.getArea();
    }
}

public class AppTest {
    public static void main(String[] args) {
        // 三角形柱体
        Triangle triangle = new Triangle(3, 4, 5);
        Cylinder cylinder1 = new Cylinder(triangle, 6);
        System.out.println("三角形柱体的体积为：" + cylinder1.getVolume());
        
        // 圆形柱体
        Circle circle = new Circle(2);
        Cylinder cylinder2 = new Cylinder(circle, 6);
        System.out.println("圆形柱体的体积为：" + cylinder2.getVolume());
        
        // 矩形柱体
        Rectangle rectangle = new Rectangle(3, 4);
        Cylinder cylinder3 = new Cylinder(rectangle, 6);
        System.out.println("矩形柱体的体积为：" + cylinder3.getVolume());
    }
}