Chapter 2

Write an application that reads two integers, determines whether the first is a multiple of the second and prints the result. [Hint: Use the remainder operator.]

Here's a peek ahead. In this chapter, you learned about integers and the type int. Java can also represent floating-point numbers that contain decimal points, such as $3.14159.$ Write an application that inputs from the user the radius of a circle as an integer and prints the circle's diameter, circumference and area using the floating-point value 3.14159 for $\pi .$ Use the techniques shown in Fig. $2.7.[$ Note: You may also use the predefined constant Math.PI for the value of $\pi$. This constant is more precise than the value $3.14159.$ Class Math is defined in package java. Tang. Classes in that package are imported automatically, so you do not need to import class Math to use it.] Use the following formulas ( $r$ is the radius): diameter $=2r$ circumference $=2\pi r$ area $=\pi r^2$ Do not store the results of each calculation in a variable. Rather, specify each calculation as the value that will be output in a System.out.printf statement. The values produced by the circumference and area calculations are floating-point numbers. Such values can be output with the format specifier \%f in a System.out.printf statement. You'll learn more about floating-point numbers in Chapter 3.

Write an application that inputs one number consisting of five digits from the user, separates the number into its individual digits and prints the digits separated from one another by three spaces each. For example, if the user types in the number 42339, the program should print Assume that the user enters the correct number of digits. What happens when you enter a number with more than five digits? What happens when you enter a number with fewer than five digits? [Hint: It’s possible to do this exercise with the techniques you learned in this chapter. You’ll need to use both division and remainder operations to “pick off” each digit.]

Using only the programming techniques you learned in this chapter, write an application that calculates the squares and cubes of the numbers from 0 to 10 and prints the resulting values in table format, as shown below.

Write a program that inputs five numbers and determines and prints the number of negative numbers input, the number of positive numbers input and the number of zeros input.

We introduced the body mass index (BMI) calculator in Exercise 1.10. The formulas for calculating BMI are $$BMI=\frac{\text{weightInPounds}\times 703}{\text{heightInInches}\times \text{heightInInches}}$$ or $$BMI=\frac{\text{weightln Kilograms}}{\text{height}\text{InMeters}\times \text{height}\text{InMeters}}$$ Create a BMI calculator that reads the user’s weight in pounds and height in inches (or, if you prefer, the user’s weight in kilograms and height in meters), then calculates and displays the user’s body mass index. Also, display the following information from the Department of Health and Human Services/National Institutes of Health so the user can evaluate his/her BMI: [Note: In this chapter, you learned to use the int type to represent whole numbers. The BMI calculations when done with int values will both produce whole-number results. In Chapter 3 you’ll learn to use the double type to represent numbers with decimal points. When the BMI calculations are performed with doubles, they’ll both produce numbers with decimal points—these are called “floating-point” numbers.]

Research several car-pooling websites. Create an application that calculates your daily driving cost, so that you can estimate how much money could be saved by car pooling, which also has other advantages such as reducing carbon emissions and reducing traffic congestion. The application should input the following information and display the user’s cost per day of driving to work: a) Total miles driven per day. b) Cost per gallon of gasoline. c) Average miles per gallon. d) Parking fees per day. e) Tolls per day.