01: Variables and Scope

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The homework

code for question 1:

/* Assume these are instance variables */
private int w = 2;
private int x;
private int y;
private int z;

/* and assume these lines happen inside the class's constructor */
x = w + x + 6;
y = 9;
z = y;
y = y / 2;

code for question 2:

int[] array1 = new int[2];
int[] array2 = new int[2];
int[] array3 = array2;
for (int i = 0; i < 2; i++) {
  array1[i] = i;
  array2[i] = i * 3;
}
array3[0] = 4;

1. (2 points) What are the values of w, x, y, and z at the end of the code above (in other words, once the constructor has executed)?

2. (5 points) Consider the second code snippet above. In the box-and-arrow style we used in class, draw the variables (array1, array2, and array3) and the arrays themselves. Label each variable with its name and type as appropriate; label the arrays with their type, and show the value stored in each cell of the arrays.

3. (1 point each) Consider a function f(m, c) = m * c * c

   a. Write a method to compute the value of such a function, given m and c. The method should have the signature double compute(double m, double c). Feel free to write this method in an IDE.

   b. How much space (in terms of the size of double values) does the JVM lay out on the stack when this method is invoked? In other words, space for how many doubles must be set aside when this method is invoked? Only consider method arguments and return values for this method, and not any others your code may call.