写一个完整的Java Application程序，包含接口ShapeArea，以及MyRectangle类，MyTriangle类和Test类

### 回答1：

public interface ShapeArea {
double getArea();
}public class MyRectangle implements ShapeArea {
private double width;
private double height;

public MyRectangle(double width, double height) {
this.width = width;
this.height = height;
} public double getArea() {
return width * height;
}
}public class MyTriangle implements ShapeArea {
private double base;
private double height; public MyTriangle(double base, double height) {
this.base = base;
this.height = height;
} public double getArea() {
return 0.5 * base * height;
}
}public class Test {
public static void main(String[] args) {
MyRectangle myRectangle = new MyRectangle(4, 5);
MyTriangle myTriangle = new MyTriangle(4, 5);
System.out.println("长方形面积：" + myRectangle.getArea());
System.out.println("三角形面积：" + myTriangle.getArea());
}
}

### 回答2：
接口ShapeArea定义：

public interface ShapeArea {
    double getArea();
}

MyRectangle类定义：

public class MyRectangle implements ShapeArea {
    private double length;
    private double width;

    public MyRectangle(double length, double width) {
        this.length = length;
        this.width = width;
    }

    @Override
    public double getArea() {
        return length * width;
    }
}

MyTriangle类定义：

public class MyTriangle implements ShapeArea {
    private double base;
    private double height;

    public MyTriangle(double base, double height) {
        this.base = base;
        this.height = height;
    }

    @Override
    public double getArea() {
        return 0.5 * base * height;
    }
}

Test类定义：

public class Test {
    public static void main(String[] args) {
        MyRectangle rectangle = new MyRectangle(5, 7);
        MyTriangle triangle = new MyTriangle(4, 6);

        System.out.println("Rectangle area: " + rectangle.getArea());
        System.out.println("Triangle area: " + triangle.getArea());
    }
}

这个Java应用程序定义了一个ShapeArea接口，以及MyRectangle类和MyTriangle类实现了该接口，并重写了getArea()方法计算矩形和三角形的面积。Test类用于测试这些类的功能，创建了一个矩形对象和一个三角形对象，并输出它们的面积。运行该程序将会打印出矩形和三角形的面积。

### 回答3：
接口ShapeArea：

public interface ShapeArea {
    double getArea();
}

MyRectangle类：

public class MyRectangle implements ShapeArea {
    private double width;
    private double height;

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

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

MyTriangle类：

public class MyTriangle implements ShapeArea {
    private double base;
    private double height;

    public MyTriangle(double base, double height) {
        this.base = base;
        this.height = height;
    }

    @Override
    public double getArea() {
        return 0.5 * base * height;
    }
}

Test类：

public class Test {
    public static void main(String[] args) {
        MyRectangle rectangle = new MyRectangle(5, 10);
        MyTriangle triangle = new MyTriangle(4, 6);

        System.out.println("矩形的面积为：" + rectangle.getArea());
        System.out.println("三角形的面积为：" + triangle.getArea());
    }
}

通过上述代码，我们定义了一个接口ShapeArea，该接口包含一个计算图形面积的方法getArea。然后我们分别实现了MyRectangle类和MyTriangle类，这两个类都实现了ShapeArea接口，并在getArea方法中分别计算了矩形和三角形的面积。最后在Test类中创建了一个MyRectangle对象和一个MyTriangle对象，并通过调用它们的getArea方法打印出它们的面积。