Write a method with the following header to display three numbers in increasing order:

public static void displaySortedNumbers(
   double num1, double num2, double num3)

Write a test program that prompts the user to enter three numbers and invokes the method to display them in increasing order.

True or false? A call to a method with a void return type is always a statement itself, but a call to a value-returning method cannot be a statement by itself.

(Display an integer reversed) Write a method with the following header to ­display an integer in reverse order:

public static void reverse(int number)

For example, reverse(3456) displays 6543 . Write a test program that prompts the user to enter an integer then displays its reversal.

(Random month) Write a program that randomly generates an integer between $1$ and $12$ and displays the English month names January, February, ... , December for the numbers $1,2, \ldots, 12$, accordingly.

(Geometry: point position) Programming Exercise 3.32 shows how to test whether a point is on the left side of a directed line, on the right, or on the same line. Write the methods with the following headers:

/** Return true if point (x2, y2) is on the left side of the
* directed line from (x0, y0) to (x1, y1) */
public static boolean leftOfTheLine(double x0, double y0,
double x1, double y1, double x2, double y2)

/** Return true if point (x2, y2) is on the same
* line from (x0, y0) to (x1, y1) */
public static boolean onTheSameLine(double x0, double y0,
double x1, double y1, double x2, double y2)

/** Return true if point (x2, y2) is on the
* line segment from (x0, y0) to (x1, y1) */
public static boolean onTheLineSegment(double x0, double y0,
double x1, double y1, double x2, double y2)

Write a program that prompts the user to enter the three points for p0 , p1 , and p2 and displays whether p2 is on the left side of the line from p0 to p1 , right side, the same line, or on the line segment. Here are some sample runs:

Enter three points for p0, p1, and p2: 1 1 2 2 1.5 1.5
(1.5, 1.5) is on the line segment from (1.0, 1.0) to (2.0, 2.0)

Enter three points for p0, p1, and p2: 1 1 2 2 3 3
(3.0, 3.0) is on the same line from (1.0, 1.0) to (2.0, 2.0)

Enter three points for p0, p1, and p2: 1 1 2 2 1 1.5
(1.0, 1.5) is on the left side of the line
from (1.0, 1.0) to (2.0, 2.0)

Enter three points for p0, p1, and p2: 1 1 2 2 1 –1
(1.0, −1.0) is on the right side of the line
from (1.0, 1.0) to (2.0, 2.0)

Write a program that calculates the average of a group of test scores, where the lowest score in the group is dropped. It should use the following functions: - void getScore () should ask the user for a test score, store it in a reference parameter variable, and validate it. This function should be called by main once for each of the five scores to be entered. - void calcAverage () should calculate and display the average of the four highest scores. This function should be called just once by main and should be passed the five scores. - int findLowest () should find and return the lowest of the five scores passed to it. It should be called by calcAverage, which uses the function to determine which of the five scores to drop. Input Validation: Do not accept test scores lower than 0 or higher than 100.

Use the methods in the following program to print 100 uppercase letters and then 100 single digits, printing ten per line.

1   public class RandomCharacter {
2       /** Generate a random character between ch1 and ch2 */
3       public static char getRandomCharacter(char ch1, char ch2) {
4           return (char)(ch1 + Math.random() * (ch2 - ch1 + 1));
5       }
6
7       /** Generate a random lowercase letter */
8       public static char getRandomLowerCaseLetter() {
9           return getRandomCharacter('a', 'z');
10      }
11
12      /** Generate a random uppercase letter */
13      public static char getRandomUpperCaseLetter() {
14          return getRandomCharacter('A', 'Z');
15      }
16
17      /** Generate a random digit character */
18      public static char getRandomDigitCharacter() {
19          return getRandomCharacter('0', '9');
20      }
21
22      /** Generate a random character */
23      public static char getRandomCharacter() {
24          return getRandomCharacter('\u0000', '\uFFFF');
25      }
26  }

(Business: check ISBN-13) ISBN-13 is a new standard for identifying books. It uses 13 digits $d_1 d_2 d_3 d_4 d_5 d_6 d_7 d_8 d_9 d_{10} d_{11} d_{12} d_{13}$. The last digit $d_{13}$ is a checksum, which is calculated from the other digits using the following formula:

$$10-\left(d_1+3 d_2+d_3+3 d_4+d_5+3 d_6+d_7+3 d_8+d_9+3 d_{10}+d_{11}+3 d_{12}\right) \% 10$$

If the checksum is $10$ , replace it with $0$ . Your program should read the input as a string. Here are sample runs:

Enter the first 12 digits of an ISBN-13 as a string: 978013213080 
The ISBN-13 number is 9780132130806

Enter the first 12 digits of an ISBN-13 as a string: 978013213079 
The ISBN-13 number is 9780132130790

Enter the first 12 digits of an ISBN-13 as a string: 97801320 
97801320 is an invalid input

Write a method with the following header to format the integer with the specified width. public static String format(int number, int width) The method returns a string for the number with one or more prefix 0s. The size of the string is the width. For example, format(34, 4) returns 0034 and format(34, 5) returns 00034. If the number is longer than the width, the method returns the string representation for the number. For example, format(34, 1) returns 34. Write a test program that prompts the user to enter a number and its width and displays a string returned by invoking format(number, width).

(Business: check ISBN-13) ISBN-13 is a new standard for identifying books. It uses 13 digits $d 1 d 2 d 3 d 4 d 5 d 6 d 7 d 8 d 9 d 10 d 11 d 12 d 13$ . The last digit d 13 is a checksum, which is calculated from the other digits using the following formula:

$$10 - (d 1 + 3d 2 + d 3 + 3d 4 + d 5 + 3d 6 + d 7 + 3d 8 + d 9 + 3d 10 + d 11 + 3d 12 ),10$$

If the checksum is 10 , replace it with 0 . Your program should read the input as a string. Here are sample runs:

Enter the first 12 digits of an ISBN-13 as a string: 978013213080
The ISBN-13 number is 9780132130806

Enter the first 12 digits of an ISBN-13 as a string: 978013213079
The ISBN-13 number is 9780132130790

Enter the first 12 digits of an ISBN-13 as a string: 97801320
97801320 is an invalid input

A regular polygon is an n-sided polygon in which all sides are of the same length and all angles have the same degree (i.e., the polygon is both equilateral and equiangular). The formula for computing the area of a regular polygon is:

$$\text { Area }=\frac{n \times s^2}{4 \times \tan \left(\frac{\pi}{n}\right)}$$

Write a method that returns the area of a regular polygon using the following header:

public static double area(1nt $\mathrm{n}$, double side)

Write a main method that prompts the user to enter the number of sides and the side of a regular polygon and displays its area.

The area of a pentagon can be computed using the following formula:

$$\text { Area }=\frac{5 \times s^2}{4 \times \tan \left(\frac{\pi}{5}\right)}$$

Write a method that returns the area of a pentagon using the following header:

public static double area(double side)

Write a main method that prompts the user to enter the side of a pentagon and displays its area.

(Print calendar) Programming Exercise 3.21 uses Zeller’s congruence to calculate the day of the week. Simplify Listing 6.12, PrintCalendar.java, using Zeller’s algorithm to get the start day of the month.

(Current date and time) Invoking System.currentTimeMillis() returns the elapsed time in milliseconds since midnight of January 1, 1970. Write a program that displays the date and time. Here is a sample run:

Current date and time is May 16, 2012 10:34:23