Review for Quiz 1

Question 1-1

In your own words, describe what distinguishes a class variable from an instance variable. (I'm not asking about how you distinguish them syntactically in Java - I'm asking how their behavior is different.)

Solution

Question 1-2

Consider the following method to compute the greatest common denominator of two numbers.

public static int sqrt(int n) {
    int x = 0;
    int d = n;
    while(d > 0) {
        if((x + d) * (x + d) <= n) x += d;
        d /= 2;
    }
    return x;
}

Say we call sqrt(32). Show how the values of x and d change as the computer continues through the method.

x
d

Solution

Question 1-3

Draw a picture of the window drawn by the following method.

import csbsju.cs160.*;

public class GraphicsExample {
    public static void run() {
        DrawableFrame window = new DrawableFrame();
        window.show();

        Graphics g = window.getGraphics();
        g.fillOval(50, 50, 100, 100);
        g.setColor(Color.white);
        g.fillRect(0, 0, 100, 200);
        g.fillOval(75, 50, 50, 50);
        g.setColor(Color.black);
        g.fillOval(75, 100, 50, 50);
        g.drawOval(50, 50, 100, 100);
    }
}

Solution

Question 1-4

Write a method that reads in a sequence of integers from the user, terminated by a 0, and displays the sum of the numbers typed. Here's an example transcript (user input in boldface).

import csbsju.cs160.*;

public class FindSum {
    public static void run() {
        // your code here...



    }
}

Solution