Question 1

Assume that x is a double that stores 0.362491. To output this value as 36%, you could use the NumberFormat class with NumberFormat nf = NumberFormat.getPercentInstance( ); Which of the following statements then would output x as 36%?

Accepted Answer

D) nf is an object and so must be passed a message to use it. The method to format a float or double is called format and the value to be formatted is the parameter passed to format. Therefore, the proper way to do this is nf.format(x). The answer in A merely outputs 0.362491 while the answers to B, C, and E are syntactically invalid.

Question 2

Which library package would you import to use the class Random?

Accepted Answer

E) This is a java numeric utility, and so is found in the java.util package.

Question 3

Which of the following would return the last character of the String x?

Accepted Answer

D) Since last is not defined, B is syntactically invalid. The 0ᵗʰ character is the first in the String, so A is True only if the String has a single character. The answer in C is syntactically invalid as length can only be called by passing the message to x. Finally, D and E are syntactically valid, but since length returns the size of the String, and since the first character starts at the 0ᵗʰ position, the last character is at x.length()-1, so E would result in a run-time error.

Question 4

For the following questions, refer to the class defined below:
import java.util.Scanner;
public class Questions
{
public static void main(String[ ] args)
{
int x, y, z;
double average;
Scanner scan = new Scanner(System.in);
System.out.println("Enter an integer value");
x = scan.nextInt( );
System.out.println("Enter another integer value");
y = scan.nextInt( );
System.out.println("Enter a third integer value");
z = scan.nextInt( );
average = (x + y + z) / 3;
System.out.println("The result of my calculation is " + average);
}
}
-What is output if x = 0, y = 1 and z = 1?

Accepted Answer

B) The division is performed as an int division since x, y, z, and 3 are all ints. Therefore, average gets the value 0.0. It is output as 0.0 instead of 0 because average is a double, which outputs at least one decimal digit unless specified otherwise using the DecimalFormat class.

Question 5

Consider the following paint method and answer the questions below:
public void paint(Graphics page)
{
page.setColor(Color.blue);
page.fillRect(50, 50, 100, 100);
page.setColor(Color.white);
page.drawLine(50, 50, 150, 150);
page.drawLine(50, 150, 150, 50);
page.setColor(Color.black);
page.drawString("A nice box", 50, 170);
}
-The figure drawn in this applet is

Accepted Answer

C) The color set before fillRect is blue, so the square is blue. The two lines are white and they are drawn from the upper left corner (50, 50) to the lower right corner (150, 150) and from the lower left corner (50, 150) to the upper right corner (150, 50).

Question 6

For the following questions, refer to the class defined below:
import java.util.Scanner;
public class Questions
{
public static void main(String[ ] args)
{
int x, y, z;
double average;
Scanner scan = new Scanner(System.in);
System.out.println("Enter an integer value");
x = scan.nextInt( );
System.out.println("Enter another integer value");
y = scan.nextInt( );
System.out.println("Enter a third integer value");
z = scan.nextInt( );
average = (x + y + z) / 3;
System.out.println("The result of my calculation is " + average);
}
}
-Questions33_34 computes

Accepted Answer

C) Because the division is an int division, even though the result is stored in a double, the resulting double may not be accurate. For instance, if x, y and z are 1, 2, and 4, the double average should be 2.33333 but average will instead be 2.00000.

Question 7

Consider the double value likelihood = 0.013885. What would be output if DecimalFormat dformatter = DecimalFormat("0.00##"); and you execute System.out.println(df.format(likelihood)); ?

Accepted Answer

B) The format "0.00##" means that at least 1 digit should appear to the left of the decimal point, even if it is 0, that at least two digits should appear to the right of the decimal point even if they are zeros, and if there are two additional digits to the right, they should also be printed, rounding the value off as needed. So, this gives 0.0139 since the number, 0.013885 will be rounded up to 0.0139.

Question 8

In order to create a constant, you would use which of the following Java reserved words?

Accepted Answer

D) The reserved word final indicates that this is the final value that will be stored in this variable, thus making it unchangeable, or constant. While constants can be of type int, constants can be of any other type as well. It is the final reserved word that makes the value unchangeable.

Question 9

Consider the following paint method and answer the questions below:
public void paint(Graphics page)
{
page.setColor(Color.blue);
page.fillRect(50, 50, 100, 100);
page.setColor(Color.white);
page.drawLine(50, 50, 150, 150);
page.drawLine(50, 150, 150, 50);
page.setColor(Color.black);
page.drawString("A nice box", 50, 170);
}
-The String "A nice box" is drawn

Accepted Answer

D) The String is drawn at coordinates (50, 170) so the x-coordinate lines up with the left-side of the box, but the y-coordinate, 170, is below the bottom edge of the box which is at y=150.

Question 10

You specify the shape of an oval in a Java applet by defining the oval's

Accepted Answer

C) The bounding box is the box that defines the height and width of the oval along with the (x, y) coordinate that are the highest and left-most point of the oval.

Question 11

What value will z have if we execute the following assignment statement?
Int z = 50 / 10.00;

Accepted Answer

E) Because 10.00 is not an int, the division produces a double precision value which cannot be stored in the int z. For this to work, the result of the division must be cast as an int before being stored in z, or the value 10.00 would have to first be cast as an int before the division takes place.

Question 12

Since you cannot take the square root of a negative number, you might use which of the following instructions to find the square root of the variable x?

Accepted Answer

C) Math.abs returns the absolute value of x. If x is negative, Math.sqrt(x) causes a run-time error, but Math.sqrt(Math.abs(x)) does not since x is first converted to its positive equivalent before the square root is performed. Answer A returns x (square root of x² is x). In answer B, casting x to an int will not resolve the problem if x is negative. In answer D, the two Math functions are performed in opposite order and so if x is negative, it still generates a run-time error. Answer E only will work if x is not positive and so if x is positive, it now generates a run-time error.

Question 13

Which library package would you import to use NumberFormat and DecimalFormat?

Accepted Answer

D) Both of these classes are used for "text processing", that is, to handle values like Strings. Such classes are found in java.text. You might think these would be in java.io, but this library has classes related to input and sending output to locations other than the monitor.

Question 14

If you want to output a double so that at least 1 digit appears to the left side of the decimal point and exactly 1 digit appears to the right side of the decimal point, which pattern would you give a DecimalFormat variable when you instantiate it?

Accepted Answer

A) The pattern "0.0" says to output all of the digits to the left of the decimal point or a 0 if there are none (you want at least 1 digit to the left, including a 0 if there are no digits) and exactly one digit to the right of the decimal point, even if the digit is 0. The patterns "0.#" and "#.#" would not output any digits to the right side of the decimal point if the value had no decimal portion (e.g., 39.0). The patterns in C and D can output up to 2 values to the right of the decimal point.

Question 15

Suppose that String name = "Frank Zappa". What will the instruction name.toUpperCase( ).replace('A', 'I'); return?

Accepted Answer

B) The toUpperCase method returns the String as all upper case characters, or "FRANK ZAPPA". The replace method will replace each instance of 'A' with 'I'.

Question 16

If you want to draw a red circle inside of a green square in an applet where the paint method is passed a Graphics object called page, which of the following sets of commands might you use?

Accepted Answer

A) You need to draw the background (larger) image first. This is the square in green. The square will be larger, so it starts at 50, 50 and is of size 100 x 100. Next, draw the circle in red inside the square, so it will start at 60, 60 and be smaller in size at 80 x 80. Answer B will accomplish the same drawings but in opposite order so that the circle is drawn over, thus blocking it as if it weren't there.

Question 17

Using getCurrencyInstance( ) formats a variable, automatically inserting

Accepted Answer

D) getCurrencyInstance will format a double or float variable so that it has 2 digits to the right of the decimal point and a dollar sign preceding the value. getPercentInstance is used to format a double or float to be output with a percent sign.

Question 18

If the String major = "Computer Science", what is returned by major.charAt(1)?

Accepted Answer

B) Neither D nor E would be correct because charAt returns a char (single character) whereas these answers are Strings. So, the question is, which character is returned? In Java, the first character of a String is numbered 0. So charAt(1) returns the second character of the String, or 'o'.

Question 19

If a, b, and c are int variables with a = 5, b = 7, c = 12, then the statement int z = (a * b - c) / a; will result in z equal to

Accepted Answer

B) (a * b - c) / a = (5 * 7 - 12) / 5 = (35 - 12) / 5 = 23 / 5, and since 23 and 5 are int values, the division is performed as an int division, or 23 / 5 = 4.

Question 20

The Random class has a method nextFloat( ) which returns a random float value between

Accepted Answer

B) The method nextFloat( ) returns a float value between 0 and 1 so that it may be used as a probability.

Quiz 2: Data and Expressions

Assume that x is a double that stores 0.362491. To output this value as 36%, you could use the NumberFormat class with NumberFormat nf = NumberFormat.getPercentInstance( ) ; Which of the following statements then would output x as 36%?