Exam 2 Review Questions

_____________The loop statement that tests the condition after executing the loop body.

_____________Guarding the data in a class from inappropriate access

_____________Adding a value to a variable

_____________When one statement is contained entirely within another statement

_____________A special method in a class that is invoked when an object is instantiated from the class

_____________A statement that uses a selector variable to choose which statements to

execute based on multiple possible values of the variable

2) What are the results of the following expressions? All of the values used in the expressions are integers. (4 pts)

a) (!(5 > 1 + 3) && (2 != 1 * (3 – 1)))

b) ((2 + 4 * 3 < 40) || (3 / 2 == 1))

3) Determine the output generated by the following program segments. If a loop is infinite, be sure to indicate this:

OUTPUT

a) int x = 5;

while (x > 0)

{

System.out.print(x + ((x – 1) + " ");

x--;

}

b) int sum = 0;

for (int x = 0; x < 7; x++)

sum = x;

System.out.println(sum);

4) Write Java statements (using loops) to accomplish the following. You need to include variable declarations and initializations in your code.

a) Print out all of the odd numbers between 1 and 20 (inclusive). Numbers should have a single space between them.

b) Read in integer numbers from the user. The user can enter any integers, positive or negative. Your code should sum the values of all positive integers and ignore the negative ones, and the loop should stop after the user has entered five positive values. The sum of those five values should be displayed.

5) Given the following class, answer the questions below:

public class Rectangle {

private int width, height;

public Rectangle()

{

width = 0;

height = 0;

}

public Rectangle(int w, int h)

{

width = w;

height = h;

}

public void setWidth(int w)

{

width = w;

}

public int getWidth()

{

return width;

}

public void setHeight(int h)

{

height = h;

}

public int getHeight()

{

return height;

}

public int calcArea()

{

return (width * height);

}

public int calcPerimeter()

{

return ((2 * width) + (2 * height));

}

public boolean isSquare()

{

boolean result;

if (width == height)

result = true;

else

result = false;

return result;

}

public String toString()

{

String result;

result = "Width: " + width + ", Height: " + height + "\n";

result += "Area: " + calcArea();

result += ", Perimeter: " + calcPerimeter() + "\n";

if (isSquare())

result += "This is a square";

else

result += "This is not a square";

return result;

}

a) Declare and instantiate a Rectangle object with width of 5 and height of 10. This should be done in a single line of code:

b) Given a Rectangle object called rect1, use the methods of the Rectangle class to compute the area and perimeter of rect1. Display these values (and only these values) to the user.

c) Given a Rectangle object called rect2, invoke the toString method (the call should be implicit).

d) Given a Rectangle object called rect3, set the width and height of rect3 to 10 and 12, respectively.

e) Given a Rectangle object called rect4, display the String “square” if rect4 is a square, and “rectangle” if rect4 is a rectangle. You must use the isSquare method.

6) What is the output of the following program segment

int x = 3, y = 4, z = 1;

z = (x - 1) * (y % 3);

if ((y > x) && (y / x < z))

System.out.print(“The if portion was executed\n”);

else

System.out.print(“The else portion was executed\n”);

Output =>

7) Write a code segment (i.e. NOT a whole program) that declares two floating point variables called x and y, reads data into these variables, then displays the two variables in DESCENDING order, regardless of the order in which they were entered. (In other words, print the bigger one out first, then the smaller one) (6 pts)

8) Write a code segment that reads in integers from the user until the user enters –1 to quit. The code should compute and return the average of the numbers. The average should be a float value. (5 pts)