root.java

国外的数据结构与算法分析用书

package dynamic_model;

/**	A class that calls some methods to show the stacking of activation records. */
public class Root
{
	public static void main(String[] arg) 
	{
		B b;
		C c = new C();
		b = c;
		b.rb(b.x);
	}
}


/**	A class with two instance variables, a constructor, and a method. */
class A
{
	public double w1, w2;

	/**	Constructor for the class. */
	public A()
	{
		w1 = 1.1;
		w2 = 1.2;
	}

	/**	A method that creates an object of type D, calls a
		method on the object, and then returns the object. */
	public D ra(D pa)
	{
		D dVar = new D(3);
		dVar.rd(pa);
		return dVar;
	}
}


/**	Descendant of A that adds an instance variable x and a method rb. */
class B extends A
{
	public D x; 

	/**	Constructor of B.  Since the constructor is empty, it can be
		removed without affecting the program. */
	public B()
	{
		// use the default initialization
	}

	/**	Initializes a local variable and calls a method inherited from A. */
	public void rb(D pb)
	{
		int intVar = 1;
		x = ra(pb);
	}
}


/**	A descendant of B that adds instance variable y and a constructor that 
	initializes the instance variables. */
class C extends B
{
	public int y;

	/**	Set the instance variables, including those inherited. */
	public C()
	{
		w1 = 3.1;
		y = 2;
		x = new D(y);
		w2 = 3.2;
	}
}


/**	A class with a constructor to initialize the instance variables and a method
	to cause a run-time error. */
class D
{
	public int z;

	/**	Constructor of the class D. */
	public D(int x)
	{
		z = x;
	}

	public void rd(D pb)
	{
		z = z / 0;
		System.out.println(z);
	}
}