请画出继承关系的UML类图，并用Java语言写出继承关系程序结构。

以下是继承关系的UML类图：

+-----------------+
|     Vehicle     |
+-----------------+
|   -maxSpeed:int |
+-----------------+
| +drive():void   |
+-----------------+

       ^
       |
+------|------+
|             |
|   Car       |  
|             |
+-------------+
| +numDoors:int|
+-------------+

以下是Java语言中的继承关系程序结构：

public class Vehicle {
    private int maxSpeed;

    public void drive() {
        System.out.println("Driving...");
    }

    public int getMaxSpeed() {
        return maxSpeed;
    }

    public void setMaxSpeed(int maxSpeed) {
        this.maxSpeed = maxSpeed;
    }
}

public class Car extends Vehicle {
    private int numDoors;

    public int getNumDoors() {
        return numDoors;
    }

    public void setNumDoors(int numDoors) {
        this.numDoors = numDoors;
    }
}

在这个例子中，Car类继承了Vehicle类。Car类拥有Vehicle类的所有属性和方法，同时也可以定义自己的属性和方法。